Vascular Anatomy of the Flower of Some Species of the Pontederiaceae*

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VASCULAR ANATOMY OF THE FLOWER OF SOME SPECIES OF THE PONTEDERIACEAE*

BY V. SINGH (School of Plant Morphology, Meerut) Received June 11, 1962 (Communicatedby Prof. V. Puti, t~.A.sc.)

INTRODUCTION

TIlE 'pickerel-weed' family Pontederiaceae is a small one of aquatic and marsh plants, comprising 6 genera with 21 species (Willis, 1951), and distributed in warmer parts of the world. The systematic position of the family has long remained one of some controversy. Engler (1886) treated it to be a member of Farinosae because of its endosperm and embryo characters. Schwartz (1930) treated it as being closely related to the Liliaceae, but also considered the dorsiventral form of the flower, the variability and reduction in the androecium and the mealy endosperm characters as of sufficient importance to justify its being placed close to the Commelinaceae and Philydraceae. Hutchinson (1934) placed the plants in the Liliales stating "The Pontederiaceae are a difficult family to place. They appear to me to be aquatic Liliaceae, tending towards the Aroid type, the spiciform inflorescence having a sheath-like reduced leaf (leaf-sheath)". Schwartz (1930) divided the family into three tribes, Eichhornieae, Heterantherae and Pontederieae, the first two with a trilocular ovary and the third with a unilocular ovary. A perusal of the literature reveals that nothing is known about the floral anatomy of this family. Therefore, at the suggestion of Professor V. Purl an investigation of the vascular anatomy of the flower of the Pontederi- aceae has been taken up. The present study deals with the Indian repre- sentatives of the family, viz., Monochoria hastaefolia Presl, Monochoria vaginal& Presl and Eichhornia crassipes Solms. The first two species belong to the tribe Heterentherae and the last to Eichhornieae. Attempts are, however, being made to procure the material of other species.

* Research contribution No. 45 from the School of Plant Morphology, Meetut College, Meerut, 339 340 V. S~GH

MATERIAL AND METHODS The material of all the three species Monochoria hastaefolia Presl, Monochoria vaginalis Presl and Eichhornia crassipes Solms was collected from Hastinapur--a place situated 23 miles north-east of Meerut (Uttar Pradesh)--in the months of April and September 1960. Flowers and flower- buds of different stages of development were preserved in formalin-acetic- alcohol. The usual customary methods of dehydration and embedding were followed. Serial transverse and longitudinal sections 10-14/, thick weIe cut and stained in crystal violet and erythrosin, which gave satisfactory results. Some floral parts cleared by sodium hydroxide, lactic acid and methyl salicylate and stained with basic fuchsin were also studied.

OBSERVATIONS Monochoria External Morphology.--The two species studied are M. hastaefolia and M. vaginalis. They are distributed throughout India and Ceylon extending to Malaya, China, Japan and tropical Africa. The plants are aquatic herbs occurring in marshy places or slow-running streams, and remain attached to the soil by means of a subterranean root stock. The root stock is spongy, elongate and creeping (M. hastaefolia) or short and suberect (M. vaginalis) clothed with brown or purple remains of the old leaf-sheaths, emitting tufts of filiform roots clothed with root hairs. The leaves are radical and solitary at the top of the emerged stems or branches, long petioled, cordate-ovate, sagittate or lanceolate, blade upraised (M. hastaefolia) or floating (M. vaginalis). Inflorescence which is always borne above water is centrifugal (M. hastaefolia) or centripetal (M. vaginalis) and reflex after flowering. The flowers are bisexual, slightly irregular, in racemes or subumbellate, arising from the sheaths of the uppermost leaves and encased by an irregular sheathing bract. The perianth is petaloid, brilliant, purplish blue with red spots, campanulate and subequally 6-partite. The segments are nearly free, the three inner ones obovate and wider than the three outer ones, all with three strong parallel median nerves and reticulately veined between them and towards the margins (Fig. 3). The stamens are six, inserted at the base of the perianth, one is large blue and five are smaller yellow. The filament of the long stamen is spurred. In M. vaginalis spurr is present on one side of the filament but in M. hastaefolia it is either present on one side (Fig. 4) or both the sides of the filament (Fig. 5). The anthers are basifixed, dehiscing introrsely by a terminal slit at length elongating. The ovary is ovoid, sessile, Vascular Anatomy of Flower of Species of Pontederiaceae 34i

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i I ! I ~6 O, mm ~ '~ 3 mm -- 3 T'orn FIos. 1-6. Figs. 1-5. Monoehoriahaataefolia. Fig. 1. Semi-diagrammaticreprescntaticn of the longitudinalsection of the flower showing vascular supply to various organs. Fig. 2. A part of the transverse section of the pedicel magnified to show air-spaces and raphides. Fig. 3. A porianth lobe cleared to show reticulate venation. Figs. 4 and 5. Stamens ,,~owing aFFcndagcs. Fig. 6. Eichhornia crasslpes. Semi;diagrammatic representation of the longitudir.al s¢ctic,n ~f the flower showing vascular supply to various organs.

3-ceUed, each cell with many anatropous ovules arranged in a double series. The style is slender, filiform; the stigma is terminal and minutely three-lobed. The fruit is a membranous loculicidal many-seeded 3-valved capsule enclosed in a persistent twisted perianth. 342 V. S~GI~ Vascular Anatomy of the Inflorescence.--The flowers of M. hastaefolia are long pediceUed arranged spirally on a short, stout, and spongy peduncle. The inflorescence axis has a large number of air spaces and numerous scattered vascular bundles. The vascular bundles are collateral with poor lignification, the xylem is very much reduced and is represented by a few tracheids. The peripheral bundles anastomose and divide to give off a large number of traces for the sheathing bract which encloses the inflorescence. On entering the bract they divide repeatedly formnig a more or less continuous band of vascular bundles. Each bundle is collateral and its xylem faces towards the inner side. There are many air chambers which alternate with the vascular bundles. Many traces for each flower pass away in a spiral manner. Vascular Anatomy of the Flower.--In a transverse section the pedicel shows a single layer of epidermis of closely fitted cells, followed by a few layers of hypodermis consisting of large thin-walled loosely packed ceils. There is a considerable amount of aerenchyma in the cortex. The air chambers are separated by one cell thick partitions (Fig. 2). In the cells of the epidermis, hypodermis and cortex occur frequently the sheaf-like bundles of long acicular calcium crystals (raphides). The vascular supply of the pedicel consists of many collateral vascular bundles with much reduced xylem as typical of hydrophytes. Apparently they may be differentiated into three whorls--outer with fourteen, middle with eight and the innermost with five bundles (Fig. 7). At the base of the receptacle the vascular bundles of the pedicel anastomose to form a more or less complete unbroken vascular cylinder in which the xylem is distinct at about six places. The saccate bases of the perianth are first to appear in cross-sections (Fig. 8). The perianth is many layered in the middle, but gradually thins out towards the margin. The epidermis is formed of thin-walled cells with irregularly lobed outline. Stomata occur on both upper and lower surface but they seem to be vestigial. The mesophyll is composed of loosely arranged parenchymatous ceils. There are also many air chambers alternating with the vascular bundles. From the receptacular stele six traces pass out simultaneously (Fig. 9). At a slightly higher level within the cortex of the receptacle each of these traces branches into three, two perianth laterals and one median conjoint perianth stamen trace that immediately branches into the perianth midrib bundle and the stamen bundle (Fig. 10). Thus, each perianth lobe receives three traces. On entcring the perianth the laterals divide to form a large number of bundles which are arranged in a single file in a transverse section. Vascular Anatomy of Flower of Species of Pontedertaceae 345

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Ftos. 7-20. Figs. 7-18. Monochoria hastaefolia. Figs. 7-16. Diagrams of serial transverse sections of the flower from base upwards. In Fig. 14 note the appendages of the stamen, In Fig. 15 except ovary other parts are omitted. Figs. 17 and 18. Transverse sections of the style and stigma respectively of the same flower. Figs. 19 and 20. Monochoria vaginalts. Trans- verse sections of the ovary and the style respectively. In Fig. 19 note the globular masses of cells in the air-c~vitics formed by the stretching of the ovary wall. 3.44 V, SINGH

However, the median bundle does not divide and remains prominent. All the bundles are endarch and collateral. Almost at the same level where carpellary dorsals depart from the central cylinder, three lacunae begin to appear outer to the three dorsals (Figs. 10, 11). These lacunae merge with one another, thus separating the corolla stamen tube from the central gynoecium part (Fig. 12). Simultaneously, spaces also appear inner to the perianth bundles separating the stamen tube from the perianth tube. The stamen tube splits up into six bits which represent the somewhat flattened bases of the filaments of the six stamens (Fig. 13). Each bit contains a single bundle which is concentric. The filament of the larger stamen has flattened appendages or outgrowths, which continue almost up to the level of the style (Fig. 14). These outgrowths are composed of homogeneous parenchymatous cells and are without any vascular supply. The single stamen bundle runs through the filament into the connective unbranched. The dithecous introrse 4-celled anthers appear just at the level of the style (Fig. 16). Raphides are scattered in the parenchymatous tissue of the stamen. Simultaneously when the perianth tube separates from the stamen tube, it splits up into six perianth segments. These are arranged in two whorls of three each (Figs. 12, 13). Soon after the departure of the perianth and stamen traces three traces pass out towards the periphery. They are the carpellary dorsals of the three carpels (Figs. 10, 11). A little higher up three locules appear one after another inner to these carpellary dorsals and the central septum begins to differentiate into massive placentae. Each placenta is vertically grooved in the middle, the grooves marking the hmits of the two halves of the placenta (Fig. 13). The remaining stelar tissue reorganises into a vascular cylinder with three prominent notches opposite the three dorsals. In this vascular cylinder xylem is facing inwards and differentiated at six places (Fig. 11). This cylinder continues as such for some distance in the centre of the ovary. Just before the point where ovules are borne it breaks up into three bundles in which the xylem faces outwards. Hence, these bundles are inversely oriented with reference to the centre of the flower. The placental strands are present on radii alternating with those of carpellary dorsals (Fig. 13). Higher up, each of these splits up into two ventrals, that still retain their inverse orientation (Fig. 13). The ovary is trilocular and in each carpel the ovules are arranged in two series, ire., half of the ovules face to one side and the remaining half to the other side. In a transverse section up to four ovules are seen on Vascular Anatomy of Flower of Species of Pontederiaceae 345 each half placenta. The two resultant ventral bundles of each fused placental strand supply the ovules of two half placentae of two adjacent carpels. Major portion of the ventral bundles is consumed in the formation of the ovular traces in the ovary region (Fig. 14). Towards the top of the ovary they disappear (Fig. 15). The carpellary dorsals do not show any branching but extend into the long style as such (Fig. 16). Before entering the stigmatic lobe each dorsal divides into two which finally disappear in the stigmatic lobe (Figs. 17, 18). The style is circular in a transverse section with three longitudinal canals extending up to the ovarian cavity. The stigmatic lobes bear many papillae-like processes (Figs. 1, 18). Raphides are scattered in the ovary wall as well as in the ovules and central axis. In the older flowers the inner epidermal layer of the ovary wall stretches from the remaining tissue and thus some air cavities are formed within the ovary wall. In M. vaginalis the flowers are with short pedicels and arranged spirally on a long axis. The vascular supply to the sheathing bract and flowers is similar to that of M. hastaefolia. The condition in M. vaginalis flower is almost similar to that of M. hastaefolia except for the number of vascular bundles in the pedicel. The number is much less in M. vaginalis and the two ventral bundles of each carpel remain fused up to the top of the ovary (Fig. 19). They divide after supplying the ovules. There is only a single longitudinal canal in the style and the stigma is without arty papillae-like processes (Fig. 20). In both the species of Monoehoria in the air cavities formed by the stretching of the inner ovary wall there are present globular masses of dark- stained cells (Fig. 19). In some cases their attachment to the ovary wall is clear. They are without any vascular supply. Eichhornia erassipes External Morphology.--It is an introduced American plant which has become widely naturalized in India in ponds, ditches, lakes and waterways. It has become a troublesome weed, difficult to eradicate, in Burma, Bengal, Orissa, and now in Uttar Pradesh also. The plant has a sympoidal rhizome creeping in mud or freely floating. The termination of each joint of the sympodium bears a rosette or broadly spoon-shaped leaves with very turN- nately swollen petioles and numerous adventitious roots. From the centre of the rosette arises sheathed scape of a dense contracted panicle. The flowers are beautiful sessile, bisexual, somewhat irregular, and liliac showy. B2 3,I6 V. SINGH

The perianth is tubular at the base, the limb spreading, slightly bilabiate with six coloured lobes. The upper lobe is larger than the rest and bears a violet blotch with a yellow centre. The stamens are six in number, irregularly inserted in the perianth tube. The three opposite the upper lip are included and those opposite the lower lip exerted. The anthers are oblong, dorsi- fixed near the base. The ovary is superior, three-celled with numerous ovules in each cell. The style is long, bent at the tip with six stigmas. The fi'uit is a three-valved many-seeded dehiscent capsule surrounded by the marcescent perianth. Vascular Anatomy of the Inflorescence.--There is a considerable amount of aerenchyma in the cortex of the inflorescence axis and a large number of scattered vascular bundles. These bundles are collateral and their xylem is reduced to a cavity with a few tracheids. The peripheral bundles of the axis anastomose and give off a large number of traces for the sheathing bract. After entering the bract the vascular bundles divide further. Thus, the bract has numerous vascular bundles arranged in two rows. The xylem of the bundles of both the rows face towards the inner side. The traces for the flower pass away in a similar way as that of M. vaginalis. Vascular Anatomy of the Flower.--The vascular supply of the pedicel consists of a large number of scattered, collateral vascular bundles with. poorly developed xylem elements (Fig. 21). There are also many air chambers in the cortex. Raphides are of frequent occurrence in the cells of the epidermis and cortex. Besides, there are a large number of tannin cells filled with small granular particles which are brown in colour, often more or less fused in masses. At the base of the flower, the vascular bundles of the pedicel undergo some anastomosis and branching and form a more or less complete ring of vascular tissue. From the central vascular cylinder three traces pass out for each perianth lobe, two lateral bundles of the perianth and one median conjoint perianth stamen trace (Figs. 22, 23). As it traverses towards the periphery of the cortex it divides into two, the outer one forms the midrib bundle of the perianth and the inner one the stamen trace (Figs. 24, 25). Thus each of the perianth lobes receives three traces. On entering the perianth the two laterals divide repeatedly. The perianth of E. crassipes presents some peculiarity in their vascular anatomy. They show a bifacial anatomy. In the midrib re~ion a number of smaller vascular bundles form an additional series (Figs. 26-28). The bundles of this series are inverted, i.e., their xylem is directed outwards facing Vascular Anatomy of Flower of Species of Pontederiaceae 347

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29 32 33 FIGs. 21-33. Eichhornia crassipes. Figs, 21-31, Diagr,qms of serial lransverse sections of the flower from base upwards, lit Fig. 29 except ovary other I~arts are omitted. Figs. 32 and 33. Transverse sections of the style and stigma respectively of the same flower. ac--air-cavities formed by the stretching of the ovary wall; ap--appendage of stamen; cpst-- conjoint perianth stamen trace; d--dorsal bundle of carpel; gin--globular masses of dark stained cells; /b--inverted bundles of the additional series; p/---lateral trace of perianth; pro--median trace of perianth; ra--raphides; sb--saccate bases of periavlh; st--stamina] trace. 348 V. S1NGH that of the outer series. These bundles continue only for a short distance and then they disappear. At about the level where carpellary dorsals diverge out some lacunae begin to appear inner to the stamen trace. All these spaces merge with one another and separate the perianth tube along with the six stamen traces, from the central gynoecium part (Fig. 27). The stamens are epiphyllous for some time. Towards the top of the ovary the filaments of the stamens start separating from the perianth tube, each with a single stamen bundle (Fig. 30). The filaments of the three stamens which lie opposite to the upper lip of the perianth are first to separate, the remaining three separate at a slightly higher level. After the separation of the filaments the perianth tube also splits up into six segments. The perianth segments are arranged in two whorls of three each. One of the perianth lobes of the inner whorl is larger than the rest (Fig. 31). Each stamen receives one trace which is concentric. The single stamen bundle runs throughout the filament unbranched and ultimately fades away in the anther.

Raphides and ta.nnin-filled cells are scattered in the parenchymatous tissue of the perianth ~nd stamens.

The stelar tissue left after the departure of the perianth and stamen traces give out three traces which enter the corresponding carpels as their dorsal bundles (Figs. 25, 26). Soon ~fter the remaining vascular tissue breaks up into three placental strands of the three carpels. These placental strands are inverted and lie on the same radii as the carpellary dorsals. Immediately, each of the three placental strands splits up into two (Fig. 26). These two- resultant ventrals of each carpel supply the ovules borne on the two half- placentae of the same carpel (cf. Monochoria hastaeJblia)(Fig. 28). The ovules are arranged in opposite direction on the two half-placentae of the same carpel. The ventral bundles confine to the placental region and after supplying the ovules, towards the top of the ovary, they disappear (Fig. 29). The carpellary dorsals pass through the style and at the base of the stigma each divides into two (Fig. 32). Thus one bundle enters into each of the six stigmas where it disappears (Fig. 33). The stigmas are covered with a large number of papillae-like processes (Figs. 6, 33). Raphides and tannin cells are scattered in the ovary wall as well as in the ovules and central axis. Vascular Anatomy of Flower of Species of Pontederiaceae 349

DISCUSSION AND CONCLUSIONS The inflorescence in case of Monochoria and Eichhornia is described as raceme or spike. The anatomical studies also support this contention. In M. hastaefolia the raceme becomes somewhat condensed so that the flowers are arranged subumbellately. The perianth is a three-traced organ. The traces of the six perianth lobes arise almost simultaneously but actually they are present in two whorls of three each. The median perianth traces arise conjointly with the stamen traces, The perianth of Monoehoria shows an unifacial anatomy with one series of normally oriented bundles. But the perianth of Eichhornia crassipes is peculiar in that it shows a biracial anatomy in the presence of a second inner series of inverted bundles. In the lamina of Eichhomia speciosa and some other species of Pontederiaceae in addition to the normally oriented bundles Arber (1920) has observed a second series of a number of strands whose xylem is inversely oriented. In her opinion (p. 344) "...... this anatomical anomaly is best interpreted on the view that the 'laminae' of Pontederiaceae instead of being homologous with the blades of Dicotyledons are merely the expanded apices of pre-existing phyllodes: the inverted bundles are thus an indication of the pefiolar nature of the organ, and are regarded as an ancestral feature rather than an adaptation". Puri (1947) has also observed an additional series of inversely oriented bundles in the sepals of Passiflora racemosa. He interpreted them as residual bundles whose major part is consumed in supplying traces for the peripheral corona. Since Pontederiaceae is the family in which we meet with phyllodic anatomy of lamina, it seems to be convincing that the bifacial anatomy of the perianth of Eichhornia crassipes indicates its phyllodic nature. Each stamen receives a single trace that is adnate with the median trace of the corolla. In Monochoria the stamens are slightly epiphyllous but in Eichhornia crassipes epiphyllous condition is pronounced and the filaments of the stamens separate from the perianth at the level of the style. In Mono- choria the filaments of the stamens remain fused at the base to form a staminal tube thus bringing about the monoadelphous condition. In Monochoria one of the stamens is larger. In taxonomic works (Hooker, 1892; Duthie, 1920; etc.) it is described that the filament of the larger stamen is toothed on one side. In the present investigation out of 200 flowers of M. hastaefolia observed by the author, 75 were found to possess appendages on both the sides of the filaments, The appendages are without any vascular 350 V. SINGH supply. Nair and Joseph (1957) have observed somewhat similar structure on the filaments of the stamens of Samadera indica. They have described them as merely the outgrowths of the filaments. In Monochoria also since these appendages are devoid of any vascular supply they can be interpreted as outgrowths of the filaments. In all the three species studied, the gynoecium is tricarpellary, trilocular with axile placentation. The vascular supply consists of six bundles-- three carpellary dorsals and three placental strands. Each placental strand divides into two ventral bundles which supply the ovules of two half-placentae. In Monochoria vaginalis the two ventrals remain fused for a considerable distance and separate only towards the top of the ovary. The carpellary dorsals extend into the style as such. Apparently, the placentation in all the three species is axile. The vascular anatomy of the flower also confirms it in case of Eichhornia crassipes. But in Monochoria the vascular anatomy is interesting and speaks something different. In both the species of Monochoria, the placentae are borne on fused margins of different carpels and derive their vascular supply from the ventrals of different carpels. The ventral bundles are inversely oriented with reference to the centre of the flower and are present on radii alternating with those of carpellary dorsals. If we consider the case of Monochoria in the light of the criteria suggested by Puri (1952) we find that the placentation is parietal except for the multilocular gynoecium and inversely oriented ventral bundles. In case of parietal placentation, Puri (1952) does not lay much emphasis on number of loculi. According to him, the multilocular condition can be brought about by the fusion of placentae among themselves. On such conditions he has interpreted the placentation of Cucurbitaceae as parietal (see Puri, 1954). In Monochoria the placental bundles are inversely oriented instead of being normally oriented as the case should have been for the parietal placentation. Such an inverse orientation of placental bundles has been observed in a number of cases of parietal pla~ntation such as Cruciferae (Gerber, 1900; Hanning, 1901; Eames and Wilson, 1928, 1929; Arber, 1931; Puri, 1941); Capparidaceae (Puri, 1950), Papaveraceae (Dickson, 1934; Arber, 1938), Moringaceae (Puri, 1942), Passifloraceae (Puri, 1945, 1947), Cucurbi- taceae (Puff, 1954), etc. Puri (1952) explains this inverse orientation of placental strands thus: "In a change from axite placentation to parietal the placental strands have shifted to the periphery, but they have still retained their inversion SO chara~teristi~ of ~xile placentation. Thus the inversion Vascular Anatomy of Flower of Species of Pontederiaceae 351 of these bundles is just a relic of past history which has somehow been retained." In Pontederiaceae in some species like Eichhornia the placentation is truly axile while in others such as Pontederia it is truly parietal. It seems that the two types of placentation merge in each other through an inter- mediate condition seen in Monochoria. The present investigation also throws some light on the nature of placenta. There has been some confusion regarding the nature of placenta. For instance, in some of the families such as Orobanchaceae and Gentianaceae each half-placenta has been described as full placenta (Hagerup, 1939; Lindsey, 1940; Tiagi, 1951). Puri (1952) following Brown (1840) considers "each placenta as composed of two ha•placentae borne on contiguous margins of the same or different carpels". He points out some distinguishing features of structure and vascular anatomy which show that each placenta is a double structure. The present observations also agree with it. In all the species studied, the placenta is a bilobed structure with the two halves distinguishable from each other. The ovules on the two halves are directed in opposite directions. Each placenta is supplied by two bundles. In Monochoria vagin.~lis the two bundles remain fused for a considerable distance and separate later on. Thus the present investigation supports the contention of Puri (1952) that each placenta is a double structure composed of two half-placentae. SUMMARY In the present paper vascular anatomy of the flower of all the three Indian species of Pontederiaceae, viz., Monochoria hastaefolia Presl, Monochoria vaginalis Presl and Eichhornia crassipes Solms is described. The perianth is a three-traced organ. In Eichhornia crassipes it is interesting since it shows a bifacial anatomy which indicates its phyllodic nature. Each stamen receives a single trace which is adnate for some distance with the median trace of the perianth. The appendages of the larger stamen of Monochoria are merely the outgrowths of the filament. The gynoecium is triearpellary syncarpous and trilocular. The vascular supply constitute of six bundles--three dorsals and three placental strands. Apparently, the placentation is axile in all the species studied. Anatomical studies also support it in case of Eichhornia crassipes. But in Monochoria, anatomically the placentation is parietal which appears to have been derived from the axile. The present investigation also gives some support to the view that each placenta is a double structure composed of two half-placentae, 352 V. SrNGH

ACKNOWLEDGEMENTS The author is deeply indebted to his esteemed teachers, Dr. Y. S. Murty, M.SC., Ph.D., F.B.S., for his valuable guidance and constant encouragement and Professor V. Purl, D.SC., F.A.SC., F.~.L, for his numerous valuable sug- gestions and continuous interest throughout the course of this study. He is also thankful to his colleagues of the School of Plant Morphology, Messrs. G. Gopal Krishna and N. P. Saxena for their help at times. Most of this work was done during the tenure of a Senior Research Training Scholarship awarded by the Ministry of Education, Government of India.

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Purl, V. .. "Studies in floral anatomy. III. On the origin and orientation of placental strands," Prec. Nat..4cad. SoL, India, 1945, 15, 74-91. .. "Studies in floral anatomy IV. Vascular anatomy of the flower of certain species of Passifloraceae," American d. Bet., 1947, 34, 562--73. .. "Studies in floral anatomy. VI. Vascular anatemy of tlae flower of Crataeva rellglosa With special reference to ff.e nature of carpels in the Capparidaceae," 1bid., 1950, 37, 363-70. .. "Placentation in angioserms," Bet. Rev., 1952, 18, 603-51. .. "Studies in floral anatomy. VII. On plac~ntation in Cureurbitaceae," Phytomorph., 1954, 4, 278-99. Schwartz, O. .. "Pontederiaceae" in Engler and Prantl Die natiirliohen Pflan. zonfamilien, Aufl~tgo 2, 1930, 15 a, 181-88. Tiagi, B. .. "Studies in the family Orobanchaceae. III. A contribution to the embryology of Orobanche cernua Loeffe. and O. aegyptiaca Pets.," Phytoraorph., 1951, 1, 158-69. Willis, J. C. .. Dictionary of Flowering Plantsand Ferns, Cambridge, 1950.

* Not seen in original.