A CONTRIBUTION TO THE EMBRYOLOGY OF SONNERATIACEAE. BY JILLELLA VENKATESWARLU. (From the Department of Botany, Benares Hi~,du U~iz,ersity, Benares.) Received April 14, 1937. (Communicated by iV[r. A. C. Joshi, M.sc.) SONNERATIACEm iS a small family of the Myrtifloreae. According to Engler and Prantl (1898, 1908), it includes four genera, Sonneratia, Duabanga, Xenodendron and Crypteronia, comprising about a dozen species. All these are found in the tropics, the monotypic genus Xenodendron being confin6d to New Guinea and the rest being mostly restricted to the Indo-Malayan region. Hutchinson (1926) in his recent system of classification has sepa- rated the genus Crypteronia into a separate family Crypteroniacem and the family Sonneratiaeem as defined by him includes only three genera. Bc:ntham a!~d I~ooker (1%2-67), on the other hand, include these genera in the family Lythracem, to which there is little doubt that these are very closely related. As the writer had been recently studying the embryology of the family Lythracem (Joshi and Venkateswarln, 1935 a, 1935 b, 1935 c, 1936), it was thought desirable to study the family Sonneratiacem also from the comparative point of view and to see how far its embryological features agree with those of the Lythracem. The previous work on this family is limited to an investigation on Sonneratia apetala Linn. by Karsten (1891). tIis observations, however, are very fragmentary and also partly erroneous as pointed out by me in preliminary notes (Venkateswarlu, 1936a, 1936b) relating to the plants described in the present paper. The present paper deals with the two chief genera of the family, namely, Duabanga and Sonneratia. The species studied are Duabanga sonnera- tioides Ham., and Sonneratia apetala Lamk. The material of the former was collected by me from plants growing in the Royal Botanical Gardens, Sibpur, Calcutta, during the months of April 1933 and May 1935 and was later supplemented by a fresh amount kindly sent by Mr. I. Banerji of Calcutta University. The material of Sonneratia apetala was collected by me in April 1936 from plants growing wild in the salt marshes near Calcutta. Material of both the plants was fixed in Nawaschin's fluid and Allen's modified Bouin's fluid. Haidenhain's iron-alum-h~ematoxylin with or with- out a counter-stain of light green was used for staining the sections. 206 ./1 Conlribution to the Em3ryoZogy of Souneraliace~ 207

Development and Structure of Pollen. The primary archesporium consists of a sub-epidermal row of cells in each of the four lobes of the anther, as may be seen from the longitudinal and transverse sections of young anthers (Figs. 1 and 2). In Sonneratia apetala there are about 10 archesporial cells in this row, in Duabanga sonne- ratioides about 20-25 cells. The first division of the primary archesporial

FIGS. 1-7. Fig. 1, D~abanga sonneratioides, longitudinal section of an anther-lobe showing the primary archesporium. Some archesporial cells near the bare have cut 'off parietal cells. Figs. 2-4, Sonneratia apetala, transverse sections of various stages in the development of an anther-lobe. Fig. 5, Sonneratia apetala, 1-nucleate pollen grain in section along tbe shorter diameter. Figs. 6-7, Duabanga sonneratioides, bi-nucleate pollen grains cut along thelonger and the shorter diameters respectively. Figs. 1 & 4, • 450 ; Figs. 2 & 3, • 600; Figs. 5--7, • 1,600. 208 Jillella Venl~ateswarlu cells is periclinal and results in an outer layer of primary parietal cells and an inner layer of primary sporogenous cells. The primary parietal ceils by periclinal divisions ultimately form 3-4 cells thick wall between the epidermis and the tapetum (Fig. 4). The inner layers of the wall are formed by narrow flattened cells which get crushed with the growth of the tapetum and sub- epidermal wall layer. The primary sporogenous cells undergo a number of divisions in all planes and give rise to a large amount of sporogenous tissue. The origin of the tapetum could not be followed definitely. Usually it consists of a single layer of cells, but sometimes here and there it is 2-seriate just as was seen in some Lythrace~e (Joshi and Venkateswarlu, 1936). At about the time when pollen-mother cell nuclei enter synizesis, the nuclei of the tapetal cells divide once mitotically, just as in the majority of other angiosperms (Cooper, 1933) and become bi-nucleate. During the formation of pollen grains, the anthers undergo the usual increase in size and the cells of the epidermis and the sub-epidermal wall layer divide anticlinally to keep pace with the general increase in size of the anther. The sub-epidermal layer in the later stages develops into the fibrous endothecium. The wall layers below it are crushed and the tapetum degenerates without forming any periplasmodium. The pollen grains separate and round off before the differentiation of intine and exine takes place. The first division of the nucleus in the pollen grains takes place after the full differentiation of intine and exine and the attainment of almost their maximum size. In Sonneratia apetala, it takes place just before the dehiscence of the anther. At the time of shedding, the pollen grains are 2-nucleate. No membrane or wall between the vege- tative and generative nuclei is seen at this stage. The mature pollen grains are "slightly elongated along one diameter. The exine is thick. The surface is smooth in Duabanga sonneratioides, while it is rather rugged in the case of Sonnera~ia apetala. Further the pollen grains of the two plants differ remarkably in size. The mature pollen grain of Duabanga sonneratioi4es measures about 16 ~ along the shorter diameter and 20/z along the longer diameter. In Sonneratia apetala it measures about 30/z along the shorter diameter and 35/~ along the longer diameter. There are 3 germ pores in the exine of each pollen grain arranged in an equatorial fashion. Their sections, therefore, along different diameters give rise to different appearances just as in Ammania baccifera (Figs. 5-7). The intine protrudes out through the germ pores. The pollen grains of Sonneratia apetala have been tested for starch, which is present in consider- able amount. A Contribution to the Embryology of SonmraEacece 209

Degenerations in the young sporogenous tissue in the anthers are quite common in Sonneratia apetala.

Structure of the G,'na~cium and the Ovule.

The ovary is semi-inferior. Usually it is described to be many-celled (10-20-celled) in Sonneratia (Engler and Prantl, 1898; Hooker, 1879, Haines, 19,~ [luring the present investigation, in Sonneratia apetala it was found to be only 5-6-celled (Fig. 8). Karsten (1391) also describes it to be 5-celled. In Duabanga sonneratioides, according to t~ngler and Prantl (1898), Hooker (1879) and Haines (1922), the ovary is 4-8-celled, but in the material examined by the writer it was found to be often up to 10-celled. In Sonneralia apetala the midribs of the carpels, which alternate with the septa, slightly protrude into the loculus of each carpel (Fig. 8), though these are not as prominent as in the ovary of Lagerstroemia (Joshi and Venkateswarlu, 19:35@ The placentas are axile and very much enlarged. There is no suggestion of a parietal or sub-basal plaeentation as described by Rendle (1925). The style is bent upon itself in bud as m some Lythraeem (Lawsonia, Neswa, Lagerstrwmia, etc.) and bears a 6-10-lobed, capitate stigma in Duabanga sonneratioides and a large, umbrella-shaped stigma in Sonneratia apetala.

In Sonneratia apetala the ovules are anatropous with a small bend in the chalazal region towards the raphe, a fact" also observed by Karsten (1891). They are also slightly flattened towards this side. The funicle is very long and in the chalazal region there is often a small space left between the outer and the inner integuments. The space may be only on one side (Fig. 10) or on both the sides (Karsten, 1891, Fig. 88). The ovules of Duabanga sonneratioides are also anatropous in their form, but they are completely cylindrical. They develop long prolongations of their integu- ments at either end, so that the seed becomes divided into a body or nucleus and two tails (Fig. 11). In Sonneratia apetala, there is no such development. In both plants, the ovules are two-integumented and ascending. However, one case was met with in Sonneratia apetala, where one of the ovnles was found to be in the orthotropons condition at the megaspore-mother cell stage, while all the neighbouring ovules had become anatropous. This ovule also deviates from the rest in only having a single integument (Fig. 9). This exactly coincides with an exceptional case observed in the case of Nescea nwrtifolia (Joshi and Venkateswarlu, 1936, Fig. 50). In Duabanga sonneratioides occasionally an ovule is found to be descending. 210 Jillella Venkateswarlu

FIGS. 8-14. ,,4 Contributiou to the Embryology of Sonneratiace~ 211

Figs. 8-10.--Sonneratia apetala. Fig. 8, transverse section of an,, overy showing 6 loculi and the carpel midribs projecting slightly into the cavities ; Fig. 9, part of Fig. 8 on a higher magnification showing an arthotropous ovule besides a normal one ; Fig. 10, longi- tudinal section of an ovule at the mature embryo-sac stage showing its form, micropyle and the air space between the two integuments near the chalaza. Figs. ll-14.--Duabanga sonneratioides. Fig. 11, longitudinal section of an ovule, showing the form, micropy'le, nucellus, conducting strand and prolongations of the integuments ; Fig. 12, transverse section of an ovule showing two nueelli within c~mm~n inner and outer integuments; Fig. 13a, longitudinal section of the upper part of an old ovule showing the long, straight mieropyle; Fig. 13b, the mieropylar part of Fig. 13a at a higher magnification showing the spiral and raticulate thiekenings of the cells composing the inner integument; Fig. 14, part of a longitudinal section of the seed-coat from the side of a seed. Fig. 8, • 12; Figs. 9 & 13a, • 64; Fig. 10, • 35; Fig. 11, • 160; Figs. 12 & 13b, • 360 ; Fig. 14, • 640.

The micropyle is formed by both the integuments, as in the Lythracem (joshi and Venkateswarlu, 1935 b, 1935 c, 1936). In Sonneratia apetala, the micropylar canal formed by the inner integument is not in a line with that formed by the outer. Thus the micropyle becomes somewhat zig-zag (Fig. 10), just as in the I,ythraceae (Joshi and Venkateswarlu, 1936). In the case of Duabanga sonneratioides, the micropylar canal, though slightly curved in the early stages, is long and perfectly straight in the later stages (Figs. 11 and 13a). Both the integuments about the time of fertilisation are 2 cells thick, except at the micropyle, where the outer integument is 3 cells thick. Their development and structure in the seed is described later. The nucellus in the ovules ready for fertilisation consists of about 5-6 layers of cells above the embryo-sac. On the sides of the embryo-sac there are about 3-4 cells in Duabanga sonneratioides and 7 or 8 cells in Sonneratia apetala. Below the embryo-sac there are about 8-10 cells in Duabanga sonneratioides and 40-50 cells in Sonneratia apetala. In this region a strand of elongated cells with rich protoplasmic contents is differ- entiated in Duabanga sonneratioides and is quite similar to the conducting strand described in the Lythracem. Such a strand of cells is not differen- tiated in Sonneratia apetala. On the other hand, there takes place a great increase in the number of cells in this region and the ovule becomes bent towards the raphe (Fig. 10). Two nucelli within an ovule have been observed in one case in Duabanga sonneratioides. In this exceptional case both the inner and outer integu- ments were common for the two nucelli (Fig. 12). Similar cases are quite common in the Lythraeem and have been seen in Cuphea lanceolata, Cu#hea petiolata (Mauritzon, 1934), Lagerstrcemia indica and Nescea" myrtifo!ia (Joshi and Venkateswarlu, 1935 c, 1936). 212 Jillella Venkateswarlu

FlCS. 15--30. Duabanga sonneratioides. A Contribution to the Embryology of Sonncratiacew 213

Figs. 15-18, primary archesporium ; Fig. 19, two rr/egaspore-mother cells in on,e ovule; Fig. 20, a nucellus with a megaspore-mother cell in the heterotypic division (metaphase) and also showing the presence of extra-nuclear karyotin bodies: Fig. 21, a nucellus showing a dyad, the upper eel1 being small and the lower being bigger; Fig. 22, a dyad with its lower ceil dividing; Fig. 23, a dyad with the upper cell dividing ; the lower ceil has already completed its division ; Fig. 24, a row of 3 megaspores, the upper being 2-nucleate ; Fig. 25, a T-shaped tetrad of megaspores ; Fig. 26, 1-nucleate embryo-sac with the nucleus in telophase ; Fig. 27, 4-nucleate embryo-sac ; Fig. 28, lower part of an embryo-sac showing the antipodal cells and the lower polar nacleus; Fig. 29, embryo-sac after the disappearance of the antipodals ; Fig. 30, a mature embryo-sac ; Figs. 15-21 and 26-30, X 640; Figs. 22-25, X 720. Development and Structure of the Embryo-sac. The number of primary arehesporial cells in an ovule is generally more than one, but occasionally in Duabanga sonneratfoides only one (Fig. 16). These cells are mostly hypodermal in origin, but occasionally sub-hypo- dermal cells are also found with archesporial characters (Figs. 15, 17, 18, 31 and 32). As in the Lythracem (Joshi and Venkateswarlu, 1035 b, 19S5 c, 1936), usually only one archesporial cell develops further, cuts off a parietal cell by a periclinal division and becomes the megaspore-mother cell. The rest of the archesporial cells merge into the ordinary nucellar cells, but in Duabanga sonneratioides the non-functional archesporial cells sometimes begin to degenerate instead of merging into the nucellus. Fig. 17 illustrates an ovule with a sub-hypodermal group of S archesporial cells, out of which one cell (on the left) is seen to degenerate. Fig. 18 shows a case of an ovule showing two hypodermal and two sub-hypodermal archesporial cells out of which the former are seen to degenerate and the latter develop further. This feature has not been observed in any Lythraceae. ~gxceptions to the above usual condition are frequently met with as in the I,ythracem. Fig. 19 shows a case of two megaspore-mother cells lying side by side in an ovule of Duabanga sonneratioides. Fig. 34 shows a similar case in Sonneratia apetala. In both the above cases, it seems that two adjacent hypodermal archesporial cells have developed and have cut off parietal cells. Fig. 35 illustrates a case of two advanced megaspore-mother cells with their nuclei in synizesis in an ovule of Sonneralia apetala. How- ever, no instances of double embryo-sacs as in some Lythrace~e (Joshi and Venkateswarlu, 1085 b, 1935 c) have been observed in these plants. The primary parietal cell first divides either antielinally or periclinally (Figs. 19 and 33). A number of anticlinal and periclinal divisions follow and make the parietal tissue 4-5 cells thick in the fully formed ovules. No tapetal layer is found to be formed around the megaspore-mother eel1. Only in Duabanga sonneratioides,, as mentioned previously, a conducting strand is developed in the chalazal region of the nucellus. 214 Jillella Venkateswarlu

FI~S. 31--46. Sonneratia apetala, A Coptlributio~ to tl~e L'mbryolor of Soz~eratiacece 215

Figs. 31-32, primary archesporium; Fig. 33, megaspore-mother cell; Figs..34 & 25, two megaspore-mother cells lying side by side; Figs. 35-38, advanced megaspore-mother cells showing the presence of the extra bodies in them; Figs. 29 & 40, linear tetrad of megaspores at different developemental stages. Fig. 41, 4-nucleate embryo-sac showing the extra body; Figs. 42 & 43, lower parts of two young embryo-sacs at different stages showing the antipodals, lower polar-nucleus and the extra body ; Fig. 44, embryo- sac after the disappearance of the antipodals with the extra body; Fig. 45, micropylar part of an embryo-sac showing egg-apparatus and the two still unfused polar nuclei near it ; Fig. 46, a mature embryo-sac. Figs. 31-.39, x 640 ; Figs. 40-46, X 360.

The megaspore-mother cell stage lasts for a long time. In Sonneratia apetala, a great increase in size is witnessed in this cell and it crushes to some extent the surrounding cells of the mmellus. The protoplasm becomes also very much vacuolated (Figs. 35-38). The nucleus, when it enters the synizesic stage, is usually found in the micropylar end of the megaspore- mother cell. The heterotypic division also consequently takes place in the micropylar region and results i,n a small upper dyad and a big lower dyad cell (Figs. 20 and 21). This recalls a similar condition observed in Wood- fordia floribunda, Neswa myrtifolia (Joshi and Venkateswarlu, 1936) and cuphea lanceolata (Mauritzon, 1934). The tetrad formation has been closely followed in Duabanga sonneratioides. The chalazal cell undergoes tile homo- typic division much earlier than the micropylar dyad cell (Figs. 22-24). The tetrad is generally linear, but sometimes in Duabanga sonneratioi~les it is T-shaped. Rarely it seems that the wall formation between tile daughter nuclei of the micropylar dyad cell fails to take place. This gives rise to a row of 3 megaspores, the uppermost being 2-nucleate and the lower two being uni-nucleate (Fig. 24). A similar case was figured by Mauritzon (193t, Fig. 1E) for Peplis portula. The chalazal megaspore of the tetrad is always the flmctional one. It is very much elongated in Sonneratia a#etala. The other megaspores are always found to degenerate. The development of the embryo-sac corresponds to the normal type. The antipodals are organised into definite cells (Figs. 28, 42 and 43). These degenerate very early and completely disappear (Figs. 29, 30, 44 and 46) by the time the polar nuclei come together as in most Lythracese. The polar nuclei meet each other about the middle of the embryo-sac, move upwards and take their position near tile egg-apparatus (Figs. 29, 44 and 45). Ulti- mately they fuse in this position to form the secondary nucleus which lies just below the egg-apparatus (Figs. 30 and 46). The movements and behaviour of the polar nuclei correspond to that exhibited by members of the Lythrace~e. The cells of the egg-apparatus also resemble those of Lythrace~e. The mature synergids bear prominent hooks and a small vacuole in their apices besides the chalazal vacuole characteristic for angiosperms ill general. 216 Jillella Venkateswarlu

The egg is flask-shaped, with a large micropylar vacuole and a small nucleus lying in the scanty cytoplasm at its chalazal end. The form and size of the embryo-sac differs in the two plants. It is broader at the ehalazal end and narrower towards the micropylar end in Duabanga sonneratioides (Fig. 30). In Sonneratia apetala, it is greatly elongated and is equally broad throughout its length (Figs. 44 and 46). At the time of fertilisation, it measures about 165/x long and about 70/~ broad (at the broadest point) in Duabanga sonneratioides, and about 250/~ long and about 40/~ broad in Sonneratia apetala. One very interesting fact about the embryo-sac of Sonneratia apetala is the presence of some extra bodies besides the nuclei. They are found to be present from the megaspore-mother cell stage to the mature embryo-sac stage. They do not stain deeply with h~ematoxylin, but remain pale. The shape of these bodies is varying (Figs. 36--46). Fig. 36 shows the presence of a single such body in a mega~pore-mother cell and Fig. 37 of 3 such bodies in an enlarged megaspore-mother cell. Sometimes these bodies have been found to be surrounded by a vacuole (Fig. 36). Fig. 38 illustrates a case of a megaspore-mother cell in which its nucleus and the body in question occupy the micropylar and ehalazal poles with a large central vacuole separating them. Further this body persists through the tetrad and other stages of the female gametophyte (Figs. 40-46). The origin and nature of these bodies could not be determined. Karsten (1891) also figures similar bodies. He described them as oily-looking. Although no such bodies are found in the embryo-sac of Duabanga sonneratioides, certain small extra-nuclear karyotin bodies staining jet black with h~ematoxylin have constantly been found to be present in the mega- spore-mother cells and dyad ceils (Figs. 20 and 21). These may be or may not be surrounded by a hyaline space. These are most probably extrusions of the nueleolus during the prophasic stages of the heterotypic division. Fertilisation, Endosperm and Development of Embryo and Seed. The above-mentioned phases of the life-history have been followed only in Duabanga sonneratioides. Fertilisation.--Karsten (1891) has made some observations on ferti- lisation in the embryo-sac of Sonneratia apetala, which differ from the results obtained in the present investigation. He found that the embryo-sac, in which fertilisation takes place, bore through the nucellus by a mieropylar projection and become situated just below the nucellar epidermis. He further states that the formation of any such aggressive process fails to take place in ovules the embryo-sacs of which are not fertilised, lie proceeds .4 Contribulion to t/ze EmSryolo#y o[ Sonneratiacew 217

to add that the pollen tube pierces through this process and advances to the egg which remains at the base of the process: This statement has also been incorporated in a recent review of fertilisation by' Dahlgren (1927). The present investigation shows Karsten's observation to be incorrect. Numerous ovules have been examined at the time of fertilisation, but no such process as observed by Karsten could be found. It appears that Karsten had mistaken the broad pollen tube to be the miCropylar process of the embryo-sac. He was. not able to see any such process in ovules in which fertilisation does not take place because in such cases it is quite natural that no pollen tubes advanced to the embryo-sacs. Some ovules with mature embryo-sacs ready for fertilisation in Sonneratia apetala have also been studied, but even a beginning of such a process could not be found in any one of them. The fertili.sation is porogamous. Normal double fertilisation takes place. The pollen tube is very broad and enters by way of the long micro- pyle. On reaching the apical end of the embryo-sac it proceeds towards one of the synergids ~nd never passes directly to the egg-cell. Tile broad end of the pollen tube presses upon the synergid and discharges its contents into it. The attacked synergid becomes filled and swollen witk dark contents (Figs: 47 and 48) and appears like a structureless mass though retaining the outer form, while the unattaeked synergld remains intact. It appears that the male nuclei always pass through the attacked synergid. The synergid breaks at its chalazal end and the contents flow o~er the eggs~ Ultimately one of the male nuclei is found tQ reach the egg nucleus and the other male nucleus reaches the secondary nucleus. The fusion of the sperm nucleus and the egg nucleus is very. slow and for a long time they remain distinct in the egg. On the other hand, the fusion between the second male nucleus and the secondary nucleus is completed earlier. The unattacked synergid degenerates and disappears, while the dark-looktM~,- structureless, attacked synergid is seen to be present until the eud~gperm is formed (Fig. 48). In this are found_often X-bodies probably representing the fragmenting synergid nucleus and the tube nucleus. Endosperm.--The development of the endosperm is similar to that found in the Lythtaceae. The primary endosperm nucleus divides r before fusion between the sperm nucleus and • egg nucleus is comple~ed. One of the daughter nuclei passes to the chalazal end, while the other goes to the micropylar end. They divide mitotically forming a number of nuclei. These remain mostly restricted to their respePcive poles and only a few migrate to the s-ides of the embryo-sac. Cytoplasm also accumulates at these poles just as in the Lythracece. On the sides it remains very thin. B4 F 218 Jillella Venkateswarlu

,~, 48

6O FIcs. 47-60. Duabangasonneratioides. ,4 Contribution to tke Embryology of Sonneratiacew 219

Figs. 47 & 48, uppen parts of longitudinal sections of two ovules showing stages in fertilisation and early stages of the developmentof the endosperm ; Fig. 49, nuclear endo- sperm with the polar accumulations; Fig. 50, longitudinal section of an embryo-sac showing cellular endosperm and an advanced embryo; Figs. 51-60, longitudinal sections of various stages in the development of the embryo; h, hypophysis ; m, mother-cell of the hypophysis. Figs. 47, 48 & 59, x 300 ; Fig. 50 X 133 ; Fig. 51, x 600 ; Figs. 49, 52-58 & 60, • 533.

The mieropylar accumulation is a little more pronounced than the chalazal one and contains a larger number of nuclei (Fig. 49). The endosperm is nuclear in early stages. During the advanced stages of the embryo-development, it becomes cellular (Fig. 50). The central cavity of the embryo-sac never gets filled up with endosperm. Embryo.--The development of the embryo is also found to agree with that of the Lythrace~e. The first division in the oospore is transverse and takes place after a number of endosperm nuclei are formed. This division is followed by one or two more transverse divisions. The pro-embryo thus becomes 3-4-celled. The terminal cell forms the embryo proper. It divides by two longi- tudinal di~'isions giving rise to the quadrants. A transverse division in each of the quadrants forms the octants (Fig. 53). Just as in the I, ythrace~e, the four superior octants later form the cotyledons and the stem tip, while the four inferior octants prodnee the hypoeotyl and the primary root except its apex. The hypophysis is formed by the superior daughter-cell of the penultimate cell of the pro-embryo. It differentiates very earl),, just as the octants are formed. The hypophysis cell is lentieular and separated from its sister cell by a curved wall. In its form and early development, along ~4th the Lythrace~e, it resembles the Onagrace~e (Souhges, 1920). The difference between the hypophysis in the Onagracem and these plants is that in the Onagracea~ the hypophysis is formed by the penultimate cell of the pro-embryo directly, while here it is formed by its superior daughter- cell only. The differentiation of the three histogenic layers proceeds as in the Lythraee~e. The dermatogen differentiates earlier in the inferior oetants by periclinal divisions (Fig. 55). The differentiation of plerome also takes place much earlier in the hypoeotyl region. The stem tip is formed very late. The hypophysis cell first divides transversely giving rise to two superposed daughter-cells, which later divide and form a plate of cells. The superior cells of this plate form the periblem of the root apex and the inferior cells form the dermatogen and the root cap. 220 Jillella Venkateswarlu

The suspensor is formed by 1 or 2 cells of the pro-embryo not taking part in the development of the embryo proper and the sister cell of the hypophysis. These cells do not seem to undergo any transverse divisions. Thus, the suspensor remains short. The suspensor cells, however, divide longitudinally, the sister cell 'of the hypophysis dividing first and the rest following it. This form of the suspensor (Fig. 60) agrees with that of species of Ammania belonging to the section Rotala (Joshi and Venkateswarlu, 1936), and Cuphea (Mauritzon, 1934). Structure of the mature seed.--The mature seed of Duabanga sonnera- tioides is a minute filiform structure measuring about 4 m.m. in length. It is prominently tailed at both the ends, each tail measuring about one-third of the whole length of the seed. The endosperm and the nucellus are destroyed completely by the growing embryo. The mature seed, therefore, is exalbuminous. The structure of the seed-coat is different in the nficropylar region from that of the rest of the body. At the sides, the cells of the outer layer of the outer integument become greatly elongated and a very darkly stain- ing stubstance, probably tannin, is densely deposited in them. The cells of the inner layer of the outer integument divide irregularly and contain some crystals. The cells of the outer layer of the inner integument remain small in size and their walls are thickened, while the cells of the inner layer increase a little in size and a certain substance is deposited in their cavities (Fig. 14). In the micropylar region, the ceils of the outer integument do not change very much, while the inner integument shows some very interesting changes. The cells of the inner layer of this integument remain narrow and elongated. A darkly staining substance, propably of the nature of tannin is deposited in them. The cells of the outer layer increase in size and dev- elop spiral and reticulate thickenings on their walls (Fig. 13b). These thicken- ings are always developed in all mature seeds of this plant. They resemble somewhat similar thickenings developed in the endothecium of the stamens in angiosperms. Similar structure of the micropyle has not been previously recorded in any other angiospermous plans nor such thiekenings have been noticed in the cells of the inner integument in any region. Such develop- ment, however, has been seen in the cells of the outer integuments, arils, caruncles and seed hairs of several plants such as Luminitzera racemosa (Karsten, 1891), Acorus (Netolitzky, 1926), etc. Conclusion, From the above account it can be at once seen that the embryological features of the family Sonneratiaceae agree even in details with those of the .4 Contrihutioz to tke Em3ryolozy olCSonneratiacew 221

Lythrace~e. The structure and development of the anther, the form and structure of mature pollen, the primary archesporium in the ovule, the development of the megaspore-mother cells (even the occasional development of more than one megaspore-mother cell), the structure and development of the nucellus, the formation of parietal tissue, the tetrads, the structure and 'development of the embryo-sac, particularly the structure of the egg-apparatus, the behavionr of polar nuclei and the early degeneration of the antipodals, the structure and formation of the endosperm (nuclear in the early stages, cellular in later stages and the formation of polar accumulations), the development of the embryo, particularly the differen- tiation of the hypophysis, and lastly the structure of the seed and testa at the sides show very striking similarities. On embryological grounds there is nothing to separate these genera from the Lythracem. Summary. The plants studied are Duabanga sonneratioides Ham. and Sonneratia a#etala Lamk. The primary archesporium in an anther-lobe consists of a hypodermal row of about 10 cells in Sonneratia and 20-25 cells in Duabanga. The anther-wall outside the tapetum is 4-5 cells thick. The tapetum is of the secretion type. The mature pollen is two-nucleate. The exine bears 3 germ pores arranged in an eqnatorial manner. Starch is abundantly seen in the mature pollen grains of Sonneratia apetala. The semi-inferior ovary is 5-6-celled in Sonneratia apetala and up to 10-celled in Duabanga sonneratioides. The ovules are numerous and borne on large axile placentas. They are anatropous, ascending, two-integu- mented and possess a moderate amount of nucellus. Both the integuments form the micropyle. The parietal tissue above the embryo-sac is 4-5 cells thick. There is a chalazal strand in the nueellus of Duabanga sonneratioides. The nucellns and consequently the ovule in the chalazal part in Sonneratia apetala shows a marked bend towards the side of the raphe. The mature ovule of Duabanga sonneratioides is prominently tailed at both of its ends. The primary archesporium generally extends to more than a single cell, but usually only one of them develops further. Occasionally two mega- spore-mother cells have been found to develop simultaneously. A linear or T-shaped tetrad is formed. The chalazal megaspore forms the embryo-sac. The development of the embryo-sac is normal. The antipodals degenerate early. The form and structure of the egg-apparatus and the behaviour of the polar nuclei corresponds to that of the Lythraceae. A peculiar pale staining body is present in the megaspore-mother cell and pers_ists even up to 222 Jillella Venkateswarlu the embryo-sac stage in Sonneratia apetala. The fertilisation is porogamous. Double fertilisati0n and triple fusion take place. No aggressive micropylar process of the embryo-sac as mentioned by Karsten is formed in either of the species studied. Endosperm is formed before the fusion of the male and the egg nuelei is complete. It is at first nuclear. Later it becomes cellular, but the central part of the embryo-sac is never filled up with cells. In the nuclear stage, the endosperm forms prominent polar accumulations. The development of the embryo is according to the Capsella-type and agrees with that of tlle Lythracem in details. The seed is exalbuminous. In the seed-coat of Duabanga, the cells of the inner integument in the region of the micropyle develop spiral and reticulate thickenings. Such a development has not been previously recorded for ally other angiospermous plant. On the whole the embryological features of the Sonneratiacem show no differences from those of the Lythracem. In conclusion, the writer wishes to express his sincere thanks to Professor A. C. Joshi for his kind interest and helpfnl suggestions during the progress of the investigation. I-Ie is indebted to Mr. I. Banerji of Calcutta University for a part of the material of Duabanga sonneratioides. He is also thankful to Dr. F. Netolitzky of Cernauti, Roumiinia, for some information about the structure of the seed-coat provided in a letter to Prof. A. C. Joshi.

LITERATURE CITED. Bentham, G., and Hooker, J. D., Genera Plantarum, I, London, 1862-67. Cooper, D.C., " Nuclear divisions in the tapetal cells of certain angiosperms," Amer. .tour. BoL, 1933, 20, 358-64. Dahlgren, K.V.O., " Die Befruchtungserscheinnngen der Angiospermen," Heredilas, 1927, 10, 169-229. Engler, A., and Prantl, K., Die niiturlichen Pflaazenfamilien, III, Tell, Leipzig, 1898. , Die natiirllchen Pflanzenfamilien, Nachtrtige fi~r 1897-1904 Zum II-IV Tell, Leipzig, 1908. Haines, H. H., The Botany of Bihar and Orissa, Part III, London, 1922. Hooker, J. D., Flora of British India, II, London, 1879. Hutchinson, J., Families of Flowering Plants--Dicotyledons, London, 1926. Joshi, A. C., and Venkateswarlu, J., "A case of reversed polarity in the embryo-sac," Ann. Bet., 1935(a), 49, 841-43. , " Embryological studies in the Lythrace~e: I--Lawsonia inermis Linn.," Prec. Ind. Acad. Sci., B, 1935(b), 2, 481-93. , "Embryologlcal studies in the Lythraee~e: II--Laeerstroemia Linn.," ibid., 1935(c), 2, 523-34.

- ., " Embryological studies in the Lythrace~e :III," ibid., 1936, 3, 377-400. A Contribution to lke Embryology of Sonneratiacew 223

Karsten, G., '" Ober die Mangrove-Vegetation in Malayischen Archipel.," Bibl. bot., 1891, 22. Mauritzon, J., "Zur Embryologie einiger Lythraceen," Meddelandcn G6teborgs Botan- iska Triidgord, 1934, 9, 1-21. Netolitzky, F., Anatomie der Angiospermensamen, Berlin, 1926. Re ndle, A. B., The Classification of Flowering Plants, Dicotyledons, Cambridge, 1925. Sou~ges, R., " Embryog6nie des Oenotherac6es. Developpement de l'embryon chez- 1" Oenothera biennis," C. R. ac. Paris, 1920, 172, 703-05. Venkateswarlu, J., " A preliminary note on the Embryology of Duabanga sonneratioides Ham.," Curr. Sci., 1936(a), 4,742-43. ," Some observations on the Ovule and Embryo-sac of Sonneratia apetal Lamk.," ibid., 1936(b), 5, 201.