d VS gee mere Dv Кык А. "чиш;

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JOURNAL

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THE LINNEAN SOCTETY.

BOTANY.

VOL. XLI.

Wo. Beat. ГОВ

| (1° LONDON:

SOLD AT THE SOCIETY'S APARTMENTS, BURLINGTON HOUSE, PICCADILLY, W., AND BY

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1912-1913.

Dates of Publication of the several Numbers included in this Volume.

No.

279, 280, 281, 289, 983, 284,

pp. 1-122, published June 28, 1912.

193-944, 945-984, 285-856, 357-490, 491-586,

November 13, 1912. December 18, 1912. July 31, 1913. October 6, 1913. December 29, 1913.

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LIST OF PAPERS.

Page BRENCHLEY, WINIFRED E., D.Sc., F.L.S.

On Branching Specimens of Lyginodendron oldhamium, Wil. (With 5 text-figures.) o... sss ems DAD

BUCKNALL, CEDRIC, Mus.Bac.Oxon,

A Revision of the Genus Symphytum, Tourn. (Communicated by Mr. J. W. Warm, F. L.S.) (With 2 text-figures.) а. 491

СнІВРЕК, H. M., М.А.

The Morphology and Histology of Piper Betle, Linn. (the Betel-vine). (Communicated by Hanonp H. Mann, D.Sc., F.L.S.) (Plates 17-19 and 1 text-figure.) |... ees BOT

Compton, Ковевт HAnonp, M.A.

An Investigation of the Seedling Structure in the Leguminose, (Com-

municated by Prof. A. C. белер, M.A., F.R.S., F.L.S.) (Plates 1-9.) 1

DE Fraine, Eruen, D.Sc., F.L.S.

The Anatomy of the Genus Salicornia. (Plates 15 & 16 and 14 text- Iu A 317

Douis, Prof. Dr. K.

Additions to the Flora of Western and North-Western Australia. (Com- municated by Dr. Отто Srapr, F.R.S., Sec.L.S.) (Plates 10-13 and 1 text-figure.) isses I eese enses is 245

Dunn, STEPHEN Troyte, B.A., F.L.S., F.R.G.S. A Revision of the Genus Millettia, Wight et Arn. ....... К 123

/

iv Page

Gipson, Prof. R. J. Harvey-, M.A., F.L.S., and MAarcery KNranr, B.Sc.

Reports on the Marine Biology of the Sudanese Red Sea.—IX. Alge (Supplement) (With 4 text-figures) ....... а 305

Groom, Percy, M.A., D.Sc., F.L.S., and W. Коѕнтох, A.R.C.S., D.I.C.

The Structure of the Wood of East Indian Species of Pinus. (Plates 24 dp EK 457

HrMsLEY, W. Воттіхс, F.R.S., F.L.S., V.M.H.

On the Genera Radamea, Bentham, and .Vesogenes, A. de Candolle. H , ?

(Plate 14)... HH memememe eee emnes 311 Koss, C. B. (See Riptey, Henry N.) Кхівнт, Mancrnv, В.е. (See Стввох, Prof. R. J. Harvey-.) Mann, Hangonp H., D.Sc., F.L.S. (See Співвев, Н. M.)

Price, M. P., M.A., and N. D. Simpson, B.A., F.R.M.S.

An Account of the Plants collected by Mr. M. P. Price on the Carruthers- Miller-Price Expedition through North-West Mongolia and Chinese Dzungaria in 1910. (Communicated by Dr. О. SrAPr, F.R.S., Sec. L.S.) (With Map and Plates 21-28.) ................... 288... 385

RipnLEv, Henry N., F.R.S., F.L.5.

An Expedition to Mount Ménuang Gasing, Selangor; with an account of the Journey by С. B. KLOSS .................. а 285

Rusuton, W. (See Groom, Percy.) SEWARD, Prof. A. C., M.A., F.R.S., F.L.S. (See Compron, В. Н.) Simpson, N. D., B.A., F.R.M.8. (See Price, M. P.)

Srapr, Dr. Orro, F.R.S., Sec.L.S. (See Domin, Prof. Dr. K., and PRICE, M. P.)

WurrE, J. W., F.L.S. (See BucKNALL, C.)

LIST OF THE PLATES.

PLATE

м J

> SEEDLING STRUCTURE IN LEGUMINOS.E.

DOR wD

ооо AJ х

=" _

м -

West AUSTRALIAN PLANTS

m [o]

14. Nesocenes Ооромти, Hemsil.

I сә

15. 16 ANATOMY OF SALICORNIA.

17.)

18. -Prper BErLE, Linn.

19. |

20. Mar or Nortu-West MONGOLIA.

91. SaussunEA Pricer, AV. D. Simpson, and LATHYRUS FROLOWII, N. D. Simpson.

99. SAUSSUREA PSEUDO-ALPINA, JV. D. Simpson, and SENECIO PRICEI, N. D. Simpson.

93. PrucepANuM Pricer, У. D. Simpson, and Poa PmicEr, N. D.

» Simpson.

24. | "INDIAN SPECIES OF PINUS. 25. |

ERRATA,

Page 113, line 10 from bottom, for leucophlma read leucophleea.

114 119 124

184 160 238

240

99

n

8, for Hornemanniaum read Hornemanuianum. 4, for NGELI read NAGEL. 13, for macrocarpa read pachycarpa. 14, for iehyochtona read ichythyochtona. 6 from bottom, for littoralis read litoralis. Т for yunnansis read yunnanensis. 8, for NizUwENnIUSII read NIEUWXENHUISIL 9, for Nieuwenhiusii read NTeuwenhuisit. 9, for Dunn read Harms. 21, for mossamibiquensis read mossambicensis, 4 from bottom, read De Wild. § Durand. 15 from bottom, for Goetzeana read Goetziana. 2 from bottom, for Sohheidei read Solheidii. П, for Valke read Vatke, 13 from bottom, for Polyosoma read Polyosma. 6 from bottom, for Pterosiphonia read Polysiphonia. 4 from bottom, for Rhodedendron read Rhododendron. 4 from bottom, for officinale read officinalis. 20, for DRABA NEMORALIS read DRABA NEMOROSA.

JuNE 28. | Price 145.

THE JOURNAL

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THE LINNEAN SOCIETY.

Vor. XLI. BOTANY. No. 279. 77.

CONTENTS.

Page An Investigation of the Seedling Structure in the Leguminose. By

Rosert НАвоір Compton, M.A., Frank Smart Student of Gonville and Caius College ; late University Frank Smart Student; Junior Demonstrator in Botany, University of Cambridge. (Communicated by Prof. A. C. Sewarp, M.A., F.R.S., F.L.S.) (Plates 1-9.)...... 1

LONDON:

SOLD AT THE SOCIETY’S APARTMENTS, BURLINGTON HOUSE, PICCADILLY, W.,

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a NER d

LINNEAN SOCIETY OF LONDON.

LIST OF THE OFFICERS AND COUNCIL. Elected 24th May, 1919.

PRESIDENT. Prof. E. B. Poulton, M.A., D.Sc., F.R.S.

VICE-PRESIDENTS.

Prof. J, Stanley Gardiner, M.A., F.R.S. Miss E. R. Saunders. Horace W. Monckton, F.G.S, Dr. D. H. Scott, F.R.S.

TREASURER. Horace W. Monckton, F.G.S.

SECRETARIES. Dr. Otto Stapf, F.R.S. | Prof. G. C. Bourne, F.R.S.

GENERAL SECRETARY. Dr. B. Daydon Jackson.

COUNCIL.

Tempest Anderson, D.Sc.

Prof. G. C. Bourne, F.R.S.

Prof. Arthur Dendy, D.Sc., F.R.S. Prof. J. Stanley Gardiner, M.A., F.R.S, Prof. Percy Groom, D.Sc,

Henry Groves, Esq.

Prof, W. A. Herdman, F.R.S.

Arthur W. Hil, M.A.

Dr. B. Daydon Jackson.

Prof. F. Keeble, Sc.D.

Horace W. Monckton, F.G.S. Prof. F. W. Oliver, F.R.S.

Prof. E. B. Poulton, F.R.S.

Dr. W. G. Ridewood.

Henry N. Ridley, F.R.S.

Miss E. R. Saunders.

Dr. Dukinfield H. Scott, F.R.S. Dr. Otto Stapf, F.R.S.

Miss Ethel N. Thomas, B.Sc. Dr. A. Smith Woodward, F.R.S.

LIBRARIAN. A. W. Kappel.

CLERK. S. Savage.

LIBRARY COMMITTEE.

The Officers ex officio, with the following in addition :—

J. Britten, Esq.

Prof. P. Groom, D.Sc. R. I. Pocock, F.R.S. Henry N. Ridley, F.R.S. R. W. Н, Row, B.Sc,

Hugh Scott, M.A.

Miss A. L. Smith.

Miss E. N. Thomas.

Dr. A. Smith Woodward, F.R.S.

THE JOURNAL

OF

THE LINNEAN SOCIETY.

(BOTANY.

An Investigation of jhe Seedling Structure in the Leguminose, Ву ROBERT Hanonp Сомртох, M.A., Frank Smart Student of Gonville and Caius College ; late University Frank Smart Student ; Junior Demonstrator in Botany, University of Cambridge. (Communicated by Prof. A. C SEWARD, M.A., F.R.S., F.L.S.)

(PLATES 1-9.)

[Read 15th February, 1912.]

CONTENTS. Page INTRODUCTION ....... kauaa aranna e ea 2 Methods ....... 0.0.00. ccc eee rss 3 Terminology... 2... 0.0.6. s 5 PART A. DETAILED DESCRIPTION ............................ 5 Mimosoideee _.......................................... 5

Acaciew (р. 5); Eu-Mimosesm (р. б); Ingem (p. 7); А депапіћегез (p. 9).

Cesalpinioidee ........................................ 10 Amherstieæ (p. 10); Bauhiniew (p. 12); Cassiex (p. 15); Eu-Ceesalpiniez (p. 18).

Papilionatie .... lees 22 Sophorezm (р. 22); Podalyriee (p. 28); Genistew (p. 25) ; Trifolie; (p. 80); Lotez (p. 35); Galegew (p. 39); Hedy- вате (р. 45); Dalbergiez (p.51); Viciee (p.52); Pha- seoleze (p. 58).

LINN. JOURN.—BOTANY, VOL. XLI, B

2 MR. R. H. COMPTON: AN INVESTIGATION OF THE

Page

Part B. SUMMARISED INFORMATION .........,‚.............. 65 Summary [48ї.......................................... 65 Introductory... 0.6. ccc cece eae 65 Summary List (with ШштЧех).......................... 68 Summaries of the different Groups ........................ 75 Part C. GENERAL DISCUSSION .............................. 89 Introductory ........... cece en 89 The Nature of the Нуросоёу] ............................ 90 Hypogeal and Epigeal Сегпіпайоп....................... 91 The Epicotyl in the Viciee .............................. 93

The Level of the Transition .............................. 96 The Level of Transition and the Mature Habit .............. 98 The Level of Transition and Phylogeny .................... 99 The Туре of Symmetry .................................. 100 Plumular Traces in Hypocotyl and Кооё.................... 101 Теїтатсһу...................... te e beeen eee 104 Reduction of the Number of Protoxylems .................. 105 Trarehy oo. cee eee hehe 106 Other Types of Бушшеїту................................ 108 The Relationships of the Types of Symmetry ............... 109 The Size of the Seedling ................................ 109 The Primitive Habit ...................... cee eee 116 Summary and Conclusions ......... ....................... 116 Bibliography 22.6.0... cee eens 1i8 Explanation of the РЇ1а{ез.................................... 120

INTRODUCTION.

Tur investigations of Seedling Anatomy published during the Nineteenth Century were largely descriptive ; their object was the establishment of morphological criteria and definitions of such concepts as the collet, hypocotyl, &c. A variety of types, culled from widely-separated groups of plants, were usually selected for examination ; with the result that a broad but vague knowledge of the anatomical tendencies of seedlings was obtained. During the past decade a new and vigorous interest has been aroused in the morphology and anatomy of juvenile forms; the stimulus being the expec- tation that a study of ontogeny will yield, in plants as in animals, valuable phylogenetic data. In the Pteridophyta this hope has been amply justified ; but in the Phanerogams, with certain notable exceptions, the results have so far been meagre and disappointing.

It has, however, been realised that the eclectic method of investigation of the Nineteenth Century must give place to the detailed study of the phenomena within systematically restricted groups of plants. In this way a great mass of information has been acquired from several circles of affinity.

Thanks to the researches of T. G. Hill and E. de Fraine (1908-1910) and

SEEDLING STRUCTURE IN THE LEGUMINOS. 3

others, we possess a considerable insight into the seedling structure of the Gymnosperms ; but the Angiosperms present a broad field of investigation, which is quite insufficiently explored.

The comprehensive researches of Goldsmith (1876), Gérard (1881), Dangeard (1889), and Chauveaud (1911), and the more special investigations of Dodel (1872), Sterckx (1900), Sargant (1903), Wright (1904), A. W. Hill (1906), T. G. Hill (1906-1908), Brandza (1909), Smith (1909), and de Fraine (1910), among other authors, have elicited much important infor- mation on the processes which occur in the transition region of the Angiosperm seedling. The extended researches of Tansley and Thomas (1904, 1906, 1907) are not yet published in full, but promise to throw much light on the problems of seedling anatomy. Except in Miss de Fraine's work on the C'actaceze, however, little has been done towards correlating the various types of seedling structure with other vegetative features.

From the standpoint of phylogeny, as well as from that of the better comprehension of anatomy, it is clearly important to determine, with as much precision as possible, what relations exist between the seedling structure and the size, form, habit, and general morphology of the species. It is with this object in view that the present investigation has been undertaken, at the suggestion of Mr. A. G. Tansley, to whom I owe a deep debt of gratitude for help and inspiration. The Leguminose were selected for study because of the great variety they display in the habit of the mature plant and in the external characters of the seedlings.

The following paper is divided into three parts :—

(A) A detailed deseription with figures of the anatomical features exhibited in the transition region of a number of species of Léguminose ; supplemented by histological and other details when occasion demands.

(B) A classified summary of the information at present available on the chief anatomical characters of the seedlings of Leguminose.

(€) A general discussion of the relations between seedling anatomy and other vegetative features, together with further facts bearing on the subject.

METHODS.

Most of the seedlings investigated were grown from seeds supplied by Mr. Irwin Lynch, Curator of the Botanic Garden, Cambridge, to whom I am deeply grateful for his unstinted kindness in obtaining seeds from many other sources. I am also much indebted to Mr. F. R. Parnell, of Mozafterpore, and Mr. F. W. South, of Barbados, for contributions of seeds.

The seeds were sown in soil at a suitable depth, and were for the most part germinated in a greenhouse. In the case of “hard” seeds, which are so

B2

4 MR. К, H. COMPTON: AN INVESTIGATION OF THE

abundant in the Leguminose, recourse was had to piercing the testa or treating the seeds with strong sulphuric acid before sowing.

The seedlings were uprooted when sufficiently grown; the standard age in the case of most epigeal species is the end of the first phase of growth, when the cotyledons are fully expanded and the plumule is as yet undeveloped. In many cases, however, the plumule develops so early that the first and second phases of growth overlap : and it is obvious that the criteria used for epigeal do not apply to hypogeal species. Therefore no constant standard founded on external appearance can be used throughout the Leguminose. Uniformity

‘can, however, be attained anatomically by describing primary vascular structures at their full development, though it frequently happens that cambial activity begins before the primary structure is fully differentiated.

The seedlings were preserved, some in 70 per cent. aleohol and some in: Carnoy's fixing fluid (transferring to spirit) ; but the best method for the present purpose was found to be simply immersion in methylated spirits, and this was adopted in the majority of cases.

The strueture was investigated by means of transverse (and occasionally longitudinal) sections. In the case of the largest seedlings these were cut by hand, but in most cases the material was embedded in paraffin and micro- tome series were prepared.

The sections were double-stained : the best results with the microtome sections were obtained by the use of Methyl Violet in 50 per cent. alcohol, followed by a solution of Erythrosin in elove-oil. Тһе seetions were cleared in clove-oil and mounted permanently in Canada balsam. For the hand- sections Methyl Violet followed by Bismarck Brown was found to give highly satisfactory results. In a few cases sections were mounted in glycerine or Schultz’s Solution: and for quick examination a one-solution mixture of Methyl Violet and Licht Grün was occasionally useful.

The work has been carried out at the Cambridge University Botany School, where I have enjoyed the facilities kindly placed at my disposal by Professor A. C. Seward.

The descriptions which follow were, in the majority of cases, prepared from an examination of several seedlings of each species. In a few instances a single specimen alone was examined, but where there is reason to think that this is not typical a note is inserted to that effect. It is probable that in some variable species, e. g. Voandzeia subterranea, Vicia Faba, examination of further specimens will supplement the account here given. In by far the greatest number of species, however, the mode of transition and the structure generally have proved extremely constant.

For the most part the transition is described, beginning at the primary root and ascending to the cotyledons. The reverse mode of description has, however, been taken into consideration, and is used for convenience in a few special instances.

SEEDLING STRUCTURE IN THE LEGUMINOSÆ. M

TERMINOLOGY.

The terms collet and external collet are used for descriptive purposes in the sense in which the latter is employed by Sterckx (1900, p. 75); i. e. as signi- fying the line of junetion between the piliferous layer and the epidermis proper.

The word hypocotyl is used to indicate that part of the axis between the cotyledonary node and the external collet. (See p. 90.)

By the term transition, as technically employed in this paper, is understood the changes which occur in the disposition of the vascular tissues only: the phenomena exhibited by other tissue-systems are outside the scope of the present study.

Parr А. DETAILED DESCRIPTION.

МІМОУОІрЕ Д, ACACIEL.E. ACACIA.

Four species of this large genus have been examined, and all show close similarity in form and structure, with slight differences in detail. The ger- mination is epigeal: the seedlings are comparatively slender, the cotyledons slightly thickened and early falling off. At the base of the hypocotyl just above the insertion of the primary root isa prominent ring or collar consisting entirely of cortical parenchyma with no special vascular system. This collar is concerned in the fixation of the seedling in the soil and in its extrication from the testa (Klebs, 1885, p. 544). It is present in many other Mimoseze and also in certain Ceesalpinioidese and Papilionate (e. g. Mimosa pudica, Leuccena glauca, Petalostylis labicheoides, Sesbania aculeata). The diameter of the hypocotyl given in the table is taken immediately above this collar.

ACACIA DORATOXYLON, A. Cunn. (РІ. 2. figs. 18-23.)

Tall shrub or small tree. Cotyledons oblong-ovate, slightly thickened.

The root contains a solid tetrarch xylem star, the protoxylems being equi- distant (fig. 18). The phloems are characterised by the presence of a central group of clear cells with scanty contents, but not fibrous ; the more densely protoplasmic tissues lying on either side of this group. Similar histological structure is exhibited by the phloem of the other Acacia spp. examined.

A parenchymatous pith begins to appear a few mm. below the external collet (fig. 19), and dilates rapidly, forcing the xylem into a tangential position. At the level of the collar the xylem is in the form of a closed ring 1-2 cells thick, enclosing a large pith, the protoxylem forming four projecting

corners (fig. 20).

©

MR. R. H. COMPTON : AN INVESTIGATION OF THE

As we ascend the hypocotyl the xylem becomes reduced in bulk and breaks along the major and minor axes of the slightly elliptical stele, separating each protoxylem into halves: thus there are produced half-way up the hypocotyl four tangential bands of metaxylem with protoxylem on their eight margins (fig. 21). The phloem remains unchanged in position, so that but for tho position of the protoxylems the stele would eontain four typical collateral bundles, In the upper half of the hypocotyl the xylem is still further reduced in bulk and becomes more endarch, and towards the cotyledonary node a pair of ordinary collateral bundles is produced at each end of the ellipse (fig. 22). These pass out without further change to the cotyledons (fig. 23). No median protoxylem is present between the two bundles of the cotyledon trace in the mature state.

ЕС-МІМОЅЕ Е.

Mimosa PUDICA, Linn.

A medium-sized shrub, with sensitive leaves *. The hypocotyl possesses at the base, just above the collet, a projecting rim or collar, which is 1:7 mm. in diameter. This is a point of agreement with the Acacieæ. The hypocotyl tapers slowly to the primary root. "The cotyledons are ovate, sagittate at the base, shortly stalked. De Candolle (1825, p. 19) gives a figure of the seedling.

The root contains four narrow 1-2-seriate xylem plates, which meet in the

entre of the stele. Тһе phloem is without fibres. А pith appears below the collet, and the four xylem plates are separated from one another; they gradually broaden internally, and at the external collet they assume the V-shape. Broadening of the xylem groups continues as we ascend the hypocotyl, and half-way up they are in the tangential position: the number of xylem elements is somewhat reduced during the transition, and the reticulate vessels are replaced by spiral. Fibres appear in the phloem in the lower part of the hypocotyl, but die away higher up.

In the upper half of the hypocotyl- the polar groups of xylem decrease considerably in bulk, and each splits into two halves. The lateral groups also divide in half, but maintain their original strength. As the node is approached the stele becomes elliptical and the halves of the lateral xylems separate widely, making room for the appearance of the plumular traces. 2 mm. below the node four bundles are found at each end of the ellipse : just above this they fuse in pairs, so that each cotyledon trace consists of two broad collateral bundles, which are now endarch. There is a short cotyle- donary tube, and small stipules are borne on the cotyledon petioles ; the cotyledons also bear the axillary buds.

A zone of small-celled collenchyma is present in the cortex, as in Acacia spp.

* The cotyledons are also sensitive, but on stimulation move upwards, whereas the. ordinary foliage leaves move downwards.

SEEDLING STRUCTURE IN THE LEGUMINOS.E, T

SCHRANKIA UNCINATA, Willd.

A perennial herb with tuberous rhizome. Hypocotyl with projecting one- sided ring at the base tapering slowly to a long primary root. ^ Cotyledons ovate.

The structure is very similar to that of Mimosa pudica, with the following differences :—Fibres are present in the primary phloem of the root. Owing to the shortness and greater diameter of the hypocotyl the changes are com- pressed as compared with Mimosa pudica, the condition at the cotyledonary node being very similar in the two cases.

LEUCÆNA GLAUCA, Benth.

A low erect tree. Hypocotyl with ring at the base, tapering slowly toa long primary root. Cotyledons ovate-oblong, cordate at base.

The root has a pith throughout, around which are present four equidistant V-shaped groups of xylem. The phloem is without fibres. At the collet ring each xylem has broken into a triad consisting of a central protoxylem and a pair of lateral metaxylems, Tannin-sacs appear here in the phloem, and a baud of thick-walled fibres extends between each phloem and the endo- dermis. The fibres decrease and the tannin-sacs increase in number as we ascend the hypocotyl. There are two zones in the cortex separated by a layer of small crushed cells (cf. Mimosa pudica, Acacia neriifolia, &c.). The epidermal cells are often prolonged into non-septate hairs.

This condition persists for about three-quarters of the length of the hypo- cotyl, the xylem gradually lessening in quantity in the polar triads, but not so much so in the lateral triads. The lateral protoxylems divide and join their respective metaxylems, which become much spread out just below the node. Each cotyledon receives four xylem bands (those derived from the lateral root-poles being much stronger than those from the polar groups) and a vestige of the polar protoxylem in the median cotyledonary plane. Each xylem band has its own phloem group.

The weakening of the polar relatively to the lateral xylems in the hypocotyl is a feature in common with the other Eu-Mimosez studied (Mimosa pudica, Schrankia uncinata) ; but Leucena glauca differs from these others in various anatomical and histological characters which are in part correlated with the superior size of the seedling.

INGE. ALBIZZIA MOLUCCANA, Miq. The following description is based on a single specimen :— Hypocotyl uniform, except for a prominent one-sided collar at its base. Cotyledons ovate. The root is tetrarch, a small pith being surrounded by a continuous ring of xylem with projecting protoxylem corners. The early stages of the transition

8 MR. R. H. COMPTON: AN INVESTIGATION OF THE

are very like those in Acacia spp. The ring of xylem enlarges in diameter and breaks at the collet region, at the protoxylems, so that four metaxylem bands are formed, each with protoxylem edges. A prominent phloem group lies exactly over each of these xylems, so that the structure is stem-like, except that the xylem is differentiated tangentially instead of centrifugally. This structure continues up the hypocotyl to within 3 mm. of the cotyledonary node. At this level a feature appears which recalls that found in some Ku-Mimosex. Each of the four xylem bands gives off a branch towards the major axis of the elliptical stele ; consequently, of the four xylem bundles supplying a cotyledon, the two inner ones are smaller than the two outer. (Cf, Mimosa pudica, Leucena glauca, &c.) Two phloem groups enter each cotyledon.

The transition phenomena thus appear to combine features characteristic of two tribes, the Acacieze and the Eu-Mimosez. А zone of thick-walled, small- celled tissue occurs in the cortex of the hypocotyl beneath the second or third subepidermal layer (Pl. 2. fig. 24). Fibres occur in the primary phloem of the hypocotyl.

PrrHECOLOBIUM SAMAN, Benth. (РІ. 9. figs. 25-28.) |

A tall tree. The hypocotyl tapers gradually to a stout primary root. The cotyledons are oblong, almost sagittate at the base, erect, fleshy, caducous. The seedling is figured by De Candolle (1825, p. 19).

The root (fig. 25) contains a good-sized pith throughout. A few mm. below the external collet the root is octarch, containing eight Y-shaped primary xylems surrounding a large pith and alternating with as many phloems. No fibres are present. Just below the collet eight protoxylems are still present, but only every other one is at all well marked; the root is in process of change to a tetrarch condition (fig. 26). Tetrarchy is attained just above the collet, the four alternate xylems having completely disappeared. The xylem is now arranged in four broad tangential bands of metaxylem with median externally projecting protoxylem points. The phloem remains in eight groups, one lying dorsally to each of the metaxylem wings; there are occasional signs, however, of the phloems fusing in pairs. The pith has now dilated very considerably, and continues to do so at the expense of the cortex as we ascend the hypocotyl. Fibres appear at the base of the hypocotyl, lying just outside the phloems. The xylem is much less bulky in the hypocotyl than at the base of the root, and continues to decrease all the way up the hypocotyl. Half-way up the hypocotyl the eight phloem groups have been reduced to four by fusion of adjacent pairs between the planes of the protoxylems. The xylems now break up—each polar xylem into a median protoxylem and a pair of metaxylems ; each lateral xylem into two groups of metaxylem with protoxylem on their adjacent edges (fig. 27). The stele then becomes somewhat elliptical, and the lateral groups separate further and

SEEDLING STRUCTURE IN THE LEGUMINOS, 9

move to join the polar groups. Immediately below the node the bundles from polar and lateral xylems respectively are almost contiguous, but they retain their individuality, and so pass out to the cotyledons ; each cotyledon receives five groups of xylem, viz. a median root protoxylem (over which the phloem is interrupted), the two polar metaxylems, and the pair of bundles derived from the lateral root xylems ; the phloem is in two long bands, which arch over the metaxylem groups (fig. 28).

The reduction of the octarehy of the root to tetrarchy in the hypocotyl i is а rare occurrence, and though constant in this species has not. been observed elsewhere in the Leguminose.

РітнесоговісМм Uneuis-cari, Benth. (Pl. 2. figs. 29-33.)

Erect shrub or tree. Hypocotyl narrowing slowly to a long primary root. Cotyledons enclosed in the testa, petiolate, sagittate at the base. Epicotyl with long tapering internode, bearing first one or two minute trifid scales and then alternate pinnate leaves.

The root contains a fair-sized pith and four similar equidistant wedges of xylem, with alternating groups of phloem (fig. 29). As we ascend towards the hypocotyl the section becomes elliptical and the xylems spread into the V-shape ; the polar groups remain continuous for some time, while the inter- cotyledonary groups separate into triads (fig. 30). At the collet the polar xylems have also divided into triads, and the metaxylems of each have fused with the adjacent metaxylems from the lateral xylem triads. The four protoxylems remain in their original positions. The phloems extend in a long band over each joint metaxylem group (fig..31). Just below the cotyle- donary node the metaxylem bands divide again with the corresponding phloem ; the original lateral metaxylems are left behind to pass into the epicotyl together with the lateral protoxylems, while each cotyledon receives only the polar triad (fig. 32). The first epicotyledonary internode contains six endarch collateral bundles, three passing to each of the first two leaves ; these are derived from the lateral root-poles (fig. 33). Thus, two of the root xylems are cotyledonary, two plumular, this including both proto- and metaxylem.

The following histological features may be noted :— The outer cortex of the root and hypocotyl contains strong collenchyma. There is a very strongly thickened perimedullary zone of fibres embedding the primary xylems.

The anatomy shows considerable differences from that of P. Saman, and may be compared rather with Cesalpinia sepiaria.

ADENANTHEREE

ADENANTHERA PAVONINA, Linn. (Pl. 2. figs. 34-37.) An erect tree. The hypocotyl narrows rather rapidly to the primary root,

10 MR. R. H. COMPTON : AN INVESTIGATION OF THE

The cotyledons are erect, large and fleshy, ovate with a cordate base. Lubbock figures the upper part of the seedling (1892, p. 469).

The root is tetrarch, containing four wedge-shaped groups of xylem surrounding a pith which is present throughout (fig. 34). 5 mm. below the external collet the metaxylem forms a continuous ring, 3—4 cells thick, round a fair-sized pith; the four protoxylems project outwards from this ring (fig. 35). The pith dilates as we ascend to the collet, and the ring of xylem becomes more extended. The phloem remains in four long ares, and no fibres are developed. In the lowest 5 mm. of the hypocotyl the amount of xylem is considerably reduced, and the ring breaks up into four triads, each comprising a median protoxylem and. a pair of metaxylem wings (fig. 36); the triads lateral to the now elliptical stele are somewhat longer tangentially than the terminal ones. The reduction in bulk of the xylem continues throughout the hypocotyl. The lateral protoxylems split and join their metaxylems just below the node. Each cotyledon receives five bundles of xylem, viz. a polar protoxylem, a pair of polar metaxylems, and a pair of lateral metaxylems witn their protoxylems attached. Тһе phloem, however, remains in two long tangential bands, the gap between them being over the polar protoxylem (fig. 37).

CAESALPINIOIDE.E. AMHERSTIE,E,

TAMARINDUS INDICA, Linn.

A large tree. The hypocotyl is uniformly thick except just below the cotyledons, where it narrows somewhat. The cotyledons are squarish-oblong, rather thick and fleshy, erect and clasping the young plumule, later caducous, stout. The axis narrows gradually below the external collet to the long and rather stout primary root. A curious feature is the early development of cork in the hypocotyl; the phellogen is situated deep in the cortex ; by the time the cotyledons have fallen eff the hypocotyl is brown, contrasting sharply with the green stem above the cotyledonary node. De Candolle (1825, p. 24) gives a figure of the seedling.

The root contains a large pith throughout. The xylem forms a continuous band surrounding the pith : this mainly consists of metaxylem, but secondary xylem develops very early; the protoxylems are four in number, but are rather feeble, and project slightly on the exterior of the metaxylem ring. The phloem is in four long bands alternating with the protoxylems. А phel- logen commences activity very early, and the cortex is quickly thrown off.

At the external collet the pith is of great size: the primary xylem is in four triads, each being composed of a small median protoxylem and a pair of metaxylems. The four triads are all similar: they are united by a continuous

SEEDLING STRUCTURE IN THE LEGUMINOS#. 11

band of secondary wood, but аге quite easy to distinguish therefrom by their slightly different reaction to stains. Four bands of phloem are present, ex- tending between the protoxylems. Very many large tannin-sacs are developed throughout the hypocotyl in the phloem and in the perimedullary zone, and also in the epidermis and two subepidermal layers.

Immediately above the collet the metaxylem begins to break up into smaller groups; about twenty of these are found throughout the greater part of the hypocotyl. They are scattered fairly evenly all round the stele, and but for the gaps in the bands of phloem and pericycle fibres it would be impossible to locate the original positions of the root protoxylems. Each eotyledon takes two bands of phloem and fibres, and a long strip of xylem tissue containing many scattered small endarch bundles.

The detailed behaviour of the vascular system is very difficult to work out, owing to the great division of the xylem groups, and because of the confusion caused by the tremendous development of tannin tissue. It seems fairly clear, however, that all the root xylem passes to the cotyledons, and that the plumular bundles do not contribute to the primary structure of the root.

TRACHYLOBIUM HoRNEMANNIANUM, Hayne.

Hypocotyl swollen at the base, rapidly narrowing to root. Cotyledons fleshy, ovate, with deep dorsal median longitudinal furrows.

The features of transition agree to a large extent with those of Tamarindus indica. The transition is low: the tetrarch root has a large pith throughout and an almost continuous ring of xylem ; triads are formed at the collet, and the hypocotyl is stem-like. It was possible here to determine definitely that the whole of the root xylem connected directly with the cotyledons.

T'annin-sacs are present in the phloem, and subepidermal secretory cavities.

SARACA CAULIFLORA, Baker.

Hypocotyl with one-sided collar at its base ; tapering rapidly to a long tap-root. Cotyledons thick, ovate, asymmetrical. - The seedling is of unusually tough consistency, owing to enormous develop- ment of. fibres in the perimedullary zone and between the phloem and endo- dermis. The details of the transition are extremely difficult to make out, owing partly to the fibres and partly to the deeply staining tannin-saes. There is little doubt, however, that the transition takes place in just the same way as in Tamarindus indica and. Trachylobium Hornemannianum,

The root is tetrarch and the transition markedly low. It may be noted that Van Tieghem and Douliot (1888, p. 173) record diarehy in Saraca (species not named).

INTSIA AFRICANA, /houars. The hypocotyl narrows rapidly to a long stout tap-root. Cotyledons fleshy.

12 MR. R. H. COMPTON: AN INVESTIGATION OF THE

The root is tetrarch, four Y-shaped xylems surrounding a large pith. Fibres present in phloem. Though only four protoxylems are prolonged into the root, a large quantity of metaxylem is present in the form of many stem-like bundles between the protoxylems: this being the arrangement so far as 1 em. below the external collet. Sections at this point show a remark- able combination of root and stem characteristics. The transition is in fact effected far below the collet. The whole of the hypocotyl has a perfect stem structure : even the root protoxylems have superposed phloem groups.

The transition is pronouncedly low, no other seedling examined surpassing it in this respect: this being doubtless correlated with its massive proportions. The general structure shows affinity with other Amherstiez.

BAUHINIEE.

BAUHINIA VARIEGATA, Linn.

A middle-sized erect tree. The hypocotyl sharply narrows to a long tap- root. Lhe cotyledons are ovate-oblong, cordate at the base, with palmate venation.

The root is tetrarch and contains a pith throughout its length. 10 mm. below the collet the xylem consists of four tangential bands with median projecting protoxylem and pairs of lateral metaxylem wings: these form a nearly continuous ring round the pith. Strong bands of fibres bound the phloem externally.

As the axis dilates below the collet the xylem ring breaks up into four isolated protoxylem groups, each with a pair of metaxylems, and usually other groups of metaxylem are left between adjacent triads. On entering the hypocotyl the lateral protoxylems also divide and join their respective metaxylem groups. All the latter acquire new internal protoxylem of their own, and so become completely endarch. Thus a stem-structure is attained at the very base of the hypocotyl and continues throughout its length.

The bulk of the xylem is reduced considerably as we ascend the hypocotyl ; the pith also increases in size and the cortex narrows considerably. Just below the node the xylem tends to collect into four main groups, two supplying each cotyledon. The polar protoxylems remain between the large cotyledonary bundles in the median plane ; and there are also a few small scattered bundles which pass out to the cotyledons between the two main groups. Each cotyledon also receives two long bands of phloem, separated only over the polar protoxylem.

BavnurxiA Ноокеві, F, Muell.

Cotyledons only just above ground. Hypocotyl narrowing slowly to a long primary root. Cotyledons ovate, slightly thickened.

The transition phenomena agree very closely with those observed in

SEEDLING STRUCTURE IN THE LEGUMINOSÆ. 13

В. variegata, except that, owing to the shortness of the hypocotyl, the changes are accelerated. The structure at the collet and cotyledonary node is very similar in the two species, but the intervening structures are tele- scoped in the bypocotyl of B. Hookeri as compared with B. variegata.

BAUHINIA ACUMINATA, Linn.

Erect shrub. Cotyledons unfolding just above ground.

The structure agrees so closely with that of other species of Bauhinia, especially B. Hookeri, that there is no need to describe it in detail.

BAUHINIA PURPUREA, Linn. (= B. triandra, Roxb.)

A middle-sized erect tree. This species is a close ally of B. variegata (p. 12), but differs markedly from that species in its mode of germination, This is half-epigeal, the cotyledons expanding somewhat beneath the ground, and turning slightly green where exposed to light. The hypocotyl is short and stout, and narrows rapidly at the external collet to a shortish primary root. The cotyledons are ovate, auricled at the base, not very thick. The epicotyl tapers upwards and the first internode is rather long *.

The structure is very similar to that of B. variegata, but owing to the shortness of the hypocotyl the transition. phenomena are somewhat compressed.

BavHINIA YUNNANENSIS, Franch.

A woody climber. The hypocotyl is of а woody consistency, narrowing rapidly to a long and little branched primary root. The cotyledons some- times remain partially buried, sometimes spread on the surface of the ground ; they are ovate in shape.

The root, a long way below the collet, is diarch, two broadly wedge-shaped groups of primary xylem being found enclosing a fair-sized pith. As we ascend to the collet the pith dilates, and the two xylems become spread out into long tangential bands arching round each end of the slightly elliptical stele. At the same time a small lateral group of xylem appears on each side of the stele: these groups at first consist wholly of metaxylem, but slightly higher up they acquire external protoxylem ; so that a transition from diarchy to tetrarchy is effected.

The phloem contains, besides sieve-tubes and companion-cells, thick-walled

* The first internode in B. purpurea. is about 30 mm. long, whereas in B. variegata it is олу 5mm. Thus the lengths of epicotyl and hypocotyl are in some degree complementary, and the first foliage leaves are carried high above the ground in both cases. Compare the epigeal Cesalpinia pulcherrima, whose first internode is about 15 mm. long, and the hypogeal C. Sappan, where it is 40 mm. long. A similar relation has been observed in Diospyros by Wright (1904, p. 61).

14 MR. R. H. COMPTON: AN INVESTIGATION OF THE

fibres and large clear cells with dark walls. The endodermis is well marked, and many of its cells are converted into tannin-saes,

As we ascend into the hypocotyl the polar bands of xylem become reduced in bulk, and each breaks up into a median protoxylem and a pair of meta- xylems: the triads so formed remain in close association, Each lateral primary xylem also divides into two halves along