Contributions to the Morphology of the Nyctaginaceae I

CONTRIBUTIONS TO THE MORPHOLOGY OF THE NYCTAGINACEAE I. Anatomy of the Node and Inflorescence of Some Species*

BY H. P. SHARMA (National Botanic Gardena, Lucknow) Received April 23, 1962 (Communicated by Dr. V. Purl, r.a.sc.)

INTRODUCTION FAMILY Nyctaginace~e comprises of about 37 genera and more than 650 species distributed mostly in the tropics and sub-tropics. It embraces plants with different habits--herbs, shrubs, trees and even climbers. The family is characterised by the presence of a single perianth whorl distin- guishable into a lower globose part, which persists in the fruit condition as an anthocarp and an upper petaloid limb. Some species are used as ornamentals but most others are wild weeds. The anatomy of the stem and abnormal secondary growth attracted the attention of botanists as early as 1849 (Schleiden). A comprehensive review of the earlier work was given by Metcalfe and Chalk (1950). Since then Inouye (1956) has done some work on the nodal anatomy of Mirabilis jalapa. Recently Nair and Nair (1961) have described the course of vascular bundles from root to the cotyledons and also in young nodes of two species of Boerhavia. A detailed and comprehensive study of the anatomy of the vegetative parts and the inflorescence has not been attempted so far. The present communication is an attempt to fill this gap.

MATERIALS AND METHODS

The present paper deals with "the anatomy of the node and inflorescence of Boerhavia repanda Willd., Boerhavia diffusa Linn., Mirabilis jalapa Linn. and Bougainvillea spectabilis Willd. All the material is readily available locally. Usual methods of dehydration and embedding were used and serial microtome sections of 10-14/, thickness were cut and stained in safranin-fast green combination.

* A major part of this work was carried out at the School of Plant Morphology, Meerut College, Moerut. 35 36 H.P. SHagMA

TIrE NODE Boerhavia repanda.--The leaves in this species are large, unequal and opposite. Bhargava (I932) noted stomata only on the lower surface. The present author has, however, noted a few on the upper surface as well. Their guard cells have cuticular ridges on the outer side. Other cells of the epidermis are wavy and the subsidiary cells are indistinguishable. The cells of the upper epidermis are somewhat longer. The petiole has three bundles arranged in an open arc. There is no 'medullary' bundle in the petiole region in this species. A little higher up, each of the lateral bundles gives out one minor branch towards the adaxial side. These continue in the pefiolar region and ultimately form the first veins of the leaf. There is a bundle sheath round the smaller veins of the lamina with large, poly- gonal, slightly thick-walled cells containing chloroplasts as also noted by Bhargava (1932).

The nodal anatomy of this species is much simpler than that of others. There are two unequal opposite and decussate leaves and three major axes at each node, the largest of which simulates the main axis and pushes out the remaining two--an inflorescence and a smaller vegetative branch--to one side (Fig. 9). Besides these axes, each leaf has one or two small buds in its axil (Fig. 8). Externally the interrelationships of the various axes at a node are not quite clear. In the sub-nodal region the parent axis contains two large arc-shaped medullary bundles in the gaps of which occur two opposite groups of leaf-trace bundles (Fig. 2). Each of these groups, in the beginning, may consist of two bundles but one of the bundles soon divides into two thus producing the normal compliment of three traces. Outside these is a pericyclic cambial ring differentiated here and there into small vascular bundles (Figs. 1-9).

As the node is approached the opposite groups of leaf traces diverge outward and, along with four prominent bundles from the peripheral ring, form a big vascular dome (Figs. 3-5). This receives a few minor traces from the peripheral vascular ring. Along with this the two medullary bundles give out two branches (Figs. 3 and 4). These move out to one side and again divide into two each (Figs. 5 and 6). Both the daughter bundles show anastomosis with inward travelling branches from the peripheral ring and their outer branches get connected to the leaf trace arc of the same side (Figs. 6 and 7). The vascular dome ultimately provides the leaf traces (Figs. 7-9). The outer branches of the medullary bundles give out the vascular supply for the next outer bud (Fig. 7). The remaining part enters Contributions to the Morphology of the NyctaginacecemI 37

~. -,o,,14

FIOS. I-!8 38 H.P. SHARMA the axillary branch itself (Figs. 8-10). The inner branches (I) of the medullary bundles ultimately form the inflorescence supply (Figs. 8 and 9). In so doing one of these divides into two thus forming the three bundles of the inflorescence axis. The remaining parts of the medullary bundles form the supply of the second axillary branch (Figs. 1 and 10). The outermost rings of the various axes on the node are contributed by the outer anastomoses. Boerhavia diffusa.--B, diffusa is a herb with many erect or procumbent branches. The leaves are opposite and petiolate. At its base, the petiole has three bundles but a little higher up the side bundles give out one minor branch each towards the adaxial side. These further break up into two each. All. these five bundles arrange themselves in the form of an adaxiaUy concave arc. There is no medullary bundle in this species also, in the petiole region (Figs. 14-18). The palisade cells surrounding a vein converge on the bundle sheath which is incomplete on the phloem side, as also reported by Bhargava (1932). The cells immediately above the lower epidermis are not collenchymatous. Like B. repanda here also at each node there are two shoots, of which one is more vigorous in growth (Figs. 16-18). Arising in between these and being pushed out to one side, is an inflorescence (Figs. 17 and 18). In between the leaf and the respective axillary shoot there are one or two smaller 'accessory' vegetative buds (Fig. 18). Anatomy of the node, in this species, is somewhat different from that of the preceding one. As usual, the stem contains a peripheral cambial ring differentiated into minor bundles here and there in the inter-nodal region (Fig. 11). Inside this ring are found some 10-12 bundles. Of these, four unequal bundles occur near the centre and have been termed as medullary bundles (Fig. 11). Between the gaps of these medullary bundles and slightly more diverged out occur two opposite groups of leaf-trace bundles, one group of which is composed of 2-3 bundles while the other has only one (Fig. 11). The remaining three bundles all occur on one side outer to the medullary bundles (Fig. 11). The median one of these three bundles occurs nearer the medullary bundle while the two lateral ones are comparatively nearer the peripheral vascular ring. As the node is approached the two smaller medullary bundles start outward migration along with the respective leaf-trace bundle (Figs. 11-I3). The latter bundle divides into two and a third branch is received from one of the smaller medullary bundles. All these three leaf-trace bundles fuse among themselves as well as with branches received from the peripheral vascular ring to form a large vascular dome (Fig. 13). This dome breaks up into three Contributions to the Morphology of the NyctaginacecemI 39 traces for the leaf and the remaining part forms the supply of the 'accessory' bud of this side (Fig. 14). The inner branches of the central bundles (I) will ultimately supply the inflorescence (Figs. 10 and 13-18). The axillary and the accessory buds of this side receive their supply from two traces. One of these is formed by one of the smaller medullary bundles (b) while the other is received as a branch from the second smaller medullary bundle of this side (Figs. 10 and 12-15). The former bundle first expands and fuses with the large medullary bundle of this side for some distance up (Figs. 10, 13 and 14). It again separates and provides intermediate bundles for the inflorescence and the axillary bud of this side. Before the separation of the bud of this side the two bundles divide into 4-5 branches. The outermost ones of these fuse together to form two large medullary bundles of the axillary bud (Figs. 10, 16 and 17). Of the remaining, two on one side and one on the opposite side form the leaf-trace bundles. The remaining two branches function as the two smaller medullary bundles. One of these will divide into two, the inner branch going to the inflorescence of this side and the outer one, along with the opposite smaller medullary bundle, will form the vascular supply of a small axillary bud of this side as was the case with similar bundles in the parent axis (Fig. 10). The three leaf-trace bundles of the other side behave in a similar manner (Figs. 13-17). The vascular supply of the main shoot and the 'accessory' bud of this side is contributed by the remaining two large medullary bundles of the parent axis. These bundles divide into two each. The daughter branches give out leaf-trace bundles of the upper node at right angles to those of the present node (Figs. 10 and 14-17). Of the remaining bundles those towards the mother axis fuse together to form the medullary bundle of the axillary shoot while those on the opposite side directly function as such (Fig. 10). After giving out branches to the leaf and axillary bud the remaining portion of the other medullary bundles (I) supplies the inflorescence the outer vascular ring of which is contributed by the large medullary bundles along with the intermediate bundles (Figs. 10 and 12-18). Mirabilis jalapa.--The plants, in this species, are stout-rooted and ascendingly branched shrubs with opposite and ovate leaves. The epidermal cells of the lamina are much wavy and the upper and lower epidermal cells are alike. The stomata are distributed on both surfaces and are of the usual type. The inflorescence is dichasially branched and is centrally placed at each node. 40 H.P. SI-tARVtA

In the sub-nodal region a transverse section of the axis shows 2--4 medullary bundles in between the gaps of which occur two opposite groups of tri-fascicular leaf-trace bundles (Figs. 19 and 20). On the outer side of the medullary bundles occur two opposite groups of small vascular bundles. Each of these groups is composed of three bundles (Figs. 20 and 21). These are surrounded by the usual pericyclic ring on the outer side. As the node is approached the three leaf-trace bundles on either side start diverging out. They receive a large number of branches from the various outer bundles in their outward course forming a dome-shaped structure as in other species (Figs. 19, 21 and 22). This vascular structure supplies the leaf and the first bud of the axillary branch of this side (Figs. 23 and 24). As the supply for these structures is differentiating the central bundles break up into two each (Figs. 19, 20 and 21). A little higher up one of the branches again breaks up into two each (Figs. 19, 21 and 22). The central branches of these (I) form the supply of the inflorescence while the side ones give out three leaf- trace bundles from their middle parts and thus breaks up into two each (Figs. 19, 24 and 25). Soon after, the opposite branches come together and fuse to form the two medullary bundles of the axillary branches (Figs. 19 and 25). It has been observed that the outer median bundles supply analogous bundles to the three major axes of the node. The same pattern of branching occurs in a decussate manner on the next node. It will be noted that here too the central bundles play the main part in supplying the various axes. Inouye (1956) has described the course of various bundles and has called the central bundles as cauline and the outer median bundles as branch bundles. The present study does not support his observations. Bougainvillea spectabilis.--The plants in this species are stout orna- mental climbers rising by means of spines. The upper epidermal cells of the leaf are straight walled while those of the lower side are somewhat rounded. There are two superposed buds in the axil of each leaf. The upper one, during the period of vegetative growth, normally develops into a spine while the lower one forms the vegetative branch. During the flowering season the upper bud forms the inflorescence. The vegetative axis between two nodes contains three medullary bundles, two unequal ones on one side and a large one opposite to these (Fig. 27). In between these and nearer the periphery are found three leaf-trace bundles on one side and two on the other but not exactly opposite (Fig. 27). Besides these and the usual peripheral procambial ring there are about nine more bundles (herein called intermediate bundles) disposed near the leaf-trace bundles (Figs. 27-29). As the node is approached the median Contributions to the Morphology of the Nyctaginaceae--I 41 trace of these diverges out first. This is followed by the lateral ones which fuse with the nearby intermediate bundles (Figs. 28-30). They ultimately supply seven traces to the petiole (Figs. 31 and 32). As the leaf traces are moving out, two of the adjacent medullary bundles divide into two each. Their inner branches fuse with some of the intermediate bundles and provide vascular traces to the main axillary bud (Figs. 29-37). A little higher up the intermediate bundles pass outward to supply vascular bundles for the smaller axillary bud which normally develops as a vegetative shoot (Figs. 31-34). The remaining portions of the medullary bundles divide again and form the vascular supply of the large axillary axis which usually develops either as an inflorescence or a spine (Figs. 33-37). More leaves and their axillary axes arise. Similarly in a 2/5 phyllotaxy (Figs. 26 and 38--40). Sometimes both the axillary axes may develop as inflorescences.

FxGs. 19-25 42 H.P. SHARMA

THE INFLORESCENCE

Boerhavia repanda.--The inflorescence in this species is much reduced and consists of five bracteate flowers arranged round a single central ebracteate one (Figs. 42--47). In the lower region the inflorescence axis bears two opposite bracts which, in their turn, bear daughter umbels. The inflorescence axis originally contains only three central bundles and the usual outer ring of minute bundles. Below the umbel-bearing region the central bundles divide into a number of branches that arrange themselves in two opposite ares and two smaller opposite bundles in between the gaps of the two arcs (Fig. 43). The latter bundles ultimately form the bract supply of the first two flowers (Figs. 43--47). Due probably to a certain amount of obliqueness the second flower appears to separate after the third and fourth flowers which appear to arise almost simultaneously and not exactly opposite to each other but slightly deflected to one side. The central bundles divide repeatedly and supply a bract trace and two more bundles (from the same gap) for each of the five flowers (Figs. 46 and 47, F1 -- Fs). After the departure of traces for the five peripheral flowers, three bundles are left in the centre, which form the supply of the single central flower (Fig. 47, C.). The outer ring of smaller bundles appears to play no significant part in the flower supply except forming homologous rings for the six pedicels.

Boerhavia diffusa.--The inflorescence axis, in this species, ends in branched sub-capitate umbels of almost sub-sessile flowers. The inflorescence axis, in a transection, has two concentric rings of vascular bundles below the umbels. Tile outer of these consists of numerous large and small bundles while the inner is formed by about five large bundles in the centre. Just below the umbel one trace diverges out from one of the inner or medullary bundles. Two more traces from the sides of the resulting gap diverge out along with the first trace (Fig. 49). All these fuse with some bundles of the outer ring forming a dome-shaped vascular structure which breaks up into two arcs as a result of the migration of the single bract trace (Fig. 49). The remaining arcs reorganise and form the supply of the axillary flower (Fig. 49). The first flower arises on one side and may bear one or two bracts with their axillant buds (Figs. 48 and 49). The second flower along with its subtending bract arises from the central axis not exactly opposite to the first but at an angle of about 147 ° (Figs. 48-51). The stalk of this too bears two bracts laterally but both these are sterile. The vascular supply of the third and the fourth flowers of the umbel arise at slightly different levels and at angles of about 140 ° and 148 ° respectively (Figs. 48, Contributions to the Morphology of the Nyctaginacece--I 43

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50 and 51). These traces in their turn form vascular rings and give out respective bract traces, The remaining tissue in the central axis forms the 44 H.P. SHARMA

supply of the fifth floral stalk which as usual bears two lateral sterile bracts. After the departure of the vascular supply for the fifth flower, the stele in the centre again reorganises and gives out a bract trace opposite the fifth flower (Figs. 48 and 51). There is no flower in the axil of this bract. The remaining central vascular tissue now directly forms the supply of the single central flower (Figs. 48, 50 and 51). Mirabilis jalapa.--The inflorescence is dichasially branched as usual, with each flower having five bracts below the calyx (Figs. 52 and 53). As already pointed out, the inflorescence axis receives two traces from the medullary bundles at each node. One of them soon divides into two, giving rise to three bundles. Further divisions in these ultimately gives rise to five bundles traversing the inflorescence axis. Five bract traces from these diverge out below the bracts (Figs. 54-58). The bract traces show some anastomosis with bundles of the outer ring (Figs. 56 and 57, br). A little higher up some minor traces from the central bundles again pass out and, along with some bundles of the peripheral ring, form an arc of minute bundles on the inner side of each bract trace (Figs. 57 and 58). The former ultimately fade away without supplying any organ. Their disposition and behaviour is suggestive of structures having been lost from the axillary positions. The floral vascular supply is thus comparable to that of an entire umbel of Boerhavia repanda (Fig. 52). Bougainvillea speetabilis.--The inflorescence is a repeatedly branched dichasial cyme and each branch terminates in a three-flowered head, arranged in a triangle (Fig. 59). The flowers remain adnate to their showy bracts for a considerable distance and are hence sessile. The axis of each flowering branch has a stele formed by two central bundles surrounded by a peripheral vascular ring with about 7--8 small bundles differentiated at various points (Fig. 60). As the floral region is approached the inner bundles divide a number of times and some of its smaller branches also fuse with bundles of the outer ring in a confused manner (Figs. 60-62). A little higher up the whole vascular tissue separates into three groups which ultimately form the respective bract and flower supply (Fig. 63). DISCUSSION In all the species studied except Bougainvillea spectabilis there are three major axes at each node, besides one or two small buds between the lateral axes and the respective leaves. In this family, the branching has generally been considered to be monopodial, As for the outermost buds, Contributions to the Morphology of the Nyctaginacece--I 45

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F1os. 42-63 46 H.P. SHARMA

they have generally been considered to be accessory in nature as no further subtending leaves are found besides the two opposite ones at each node. In Phytolacacem (author's unpublished observations) a small structure has been seen in between the outermost bud and the normal vegetative leaves. These are evidently prophylls and the buds they subtend are also prophyUar in nature. In the Nyctaginace~e, which has often been related to Phyto- lacace~e, even though the prophylls are absent the outermost buds appear to be prophyllar in nature. Of the three major axes just referred to, the median one, in all the species studied, forms the inflorescence. In Mirabilis jalapa, the two medullary bundles give out one branch each from the centre, which ultimately forms the vascular supply of the centrally situated inflorescence. In Boerhavia repanda the vascular supply of the inflorescence arises fused with that of the weaker lateral shoot and separates therefrom a little higher up. The inflorescence, in this case, gets pushed out to one side and is no longer centrally placed. In Boerhavia diffusa also the inflorescence supply arises fused with that of the side shoot. Here, however, only one bundle goes to the inflorescence. The second bundle from the opposite side is completely missing. Further, the fusion between the vascular bundles of the lateral shoot and those of the inflorescence is much greater and like B. repanda the latter is again pushed out to one side. From this .it is clear that the inflorescence, in these species, is really the terminal part of the main axis while the two unequal lateral shoots are of equal status and hence axillary in nature. The fact that one of these is much stronger coupled with the external position of the inflorescence completely masks this fact. It thus appears that the branching in these species is sympodial.* In Bougainvillea, the position is entirely different. In this species, the main axis is continuous bearing leaves in 2/5 phyllotaxy (Fig. 26). The main axillary branches, in this case, end either as spines or as inflorescences. Further buds continue to grow as vegetative shoots. There is some difference between the vascular supply of the axillary structures in Bougainvillea and other species studied. In the latter, all the axillary axes receive their supply mainly from the medullary bundles while in Bougainvillea only the main axillary bud (i.e., the inflorescence) receives traces from the medullary bundles and the outer buds receive theirs mainly from the intermediate bundles. Whatever branches they receive from the medullary bundles only go to form the intermediate bundles of these axes.

* After this communication had gone to press Pant & Mehra (Phytomcrphology, 1962, 11, 384--405) have described the nodal anatomy of Boerhavia diffusa interpreting the irdior- escenoe as extra axillary and the minute buds between the main axillary axes and the subtending leaves as accessory. Contributions to the Morphology of the Nyctaginaceae--I 47

Nair and Nair (1961) have shown the independence of the medullary bundles in B. diffusa from node to node. As is clear from the present studies this is not the case at least in older nodes. From Text-Fig. 10 it is evident that the various bundles of a shoot are interconnected at various nodes. In Bougainvillea, comparatively, there is greater independence of the bundles supplying consecutive leaves. But here also one of the lateral bundles of each leaf arises from the fusion product of two adjoining medullary bundles. In the two Boerhavias studied there are five flowers grouped round a central one (Figs. 42 and 48). In B. diffusa the central flower has a bract opposite the fifth flower. Besides, the floral traces arise at different levels and in a definite order. In B. repanda, however, all the flowers as well as their vascular supply appear to arise at the same level. Further, there are no bracteoles on the individual flowers and the bract on one side of the central flower is also missing. All these facts suggest that in this family, originally the inflorescence axis bore single dichasial units for six successive nodes probably in a 2/5 phyllotaxy before ending in a single central flower. A somewhat similar inflorescence has been observed in some Portulacace~e (Sharma, 1958). The least modification in this plan is shown by Boerhavia diffusa in which the six nodes are condensed to an extent where externally all the flowers appear to arise almost at the same level. Their vascular traces, however, clearly show the intervening nodes. Besides this, one of the flowers of the uppermost node (opposite the fifth flower) got completely suppressed leaving only the subtending bract intact. Similarly, the lateral flower of the dichasial units have also started showing suppression leaving only the bracteoles still present. Boerhavia repanda shows still greater condensation. In this case, all the units of the floral head as well as their vascular supply arise from the same level. Besides, along with the sixth bract the bracteoles on the peripheral flowers are also missing.

The inflorescence of Bougainvillea spectabilis has only three flowers in the head, though lower down, it shows dichasial branching repeatedly with the central branches ending in a three-flowered head (Fig. 59). It is tempting to conclude that the floral heads here represent the terminal dichasia of each central axis. However, the fact that each head arises in the axil of a bract and again, each flower of the head in its turn arises fused with a subtending bract clearly proves that none of these flowers occupies the central position and all the three flowers are only the lateral structures. Eichler (1878) also came to a somewhat similar conclusion as seen from his diagrams. On comparison with Boerhavia this plant shows still greater 48 H.P. SnARMA condensation and suppression. Here, along with the central flower three of the nodes are also completely suppressed. Further, no trace of the lateral bracteoles of each flower is left. In Mirabilis jalapa, on the other hand, only the central flower has remained while all the lateral flowers have been lost through reduction. However, their bracts as also the vascular stubs of the missing central flowers are still persisting for some distance up. In other species of Mirabilis (like M. multiflora) there are more than one flower in each head. Joshi and Rao (1934) reported a very significant variation in a flower of Boerhavia repanda. In this flower these authors observed an involucre of five bracts without any axillary flowers in their axils. This clearly supports the above conclusions and shows that the apparently single flower of Mirabilis jalapa is in fact comparable to an umbel of Boerhavia repanda.

SUMMARY Anatomy of the node and inflorescence of four species of the family Nyctaginace~e has been described. Some difference in the vascular supply of these structures in different species has been noted. In all the species studied here, except Bougainvillea spectabilis, there are two unequal and opposite leaves and three major axes at each node the interrelationships of which are not quite clear externally. It has been concluded that in all the species studied here except Bougainvillea spectabilis, the inflorescence represents the terminal part of the main axis while the two unequal major vegetative shoots at each node are really the axillary buds. Further buds in the axil of the leaves are probably prophyllar in nature. In Bougainvillea spectabilis the leaves are arranged in a 2/5 phyllotaxy and their main axillary shoots develop as inflorescences while the main axis is continuous. On the basis of a difference in the origin of the vascular supply between the various flowers in an umbel it has been suggested that originally the inflorescence axis, in this family, probably bore single dichasial units for six nodes before ending in a central flower. Presence of a very similar inflorescence in some Portulacace~e lends support to this. Reduction in the lateral flowers and the attended condensation between various nodes of such an inflorescence has given rise to the umbel of Boerhavia cliffusa. B. repanda shows further reduction with all the flowers Contributions to the Morphology of the Nyctaginacece--I 49 arising at the same level. In Mirabilis jalapa only the central flower persists while the peripheral ones are suppressed, leaving only their subtending bracts and some vascular stubs in the inflorescence axis. In Bougainvillea the central flower is completely suppressed leaving only three peripheral flowers in each head.

ACKNOWLEDGEMENTS The author is deeply indebted to Prof. V. Purl, D.SC., F.A.SC., F.N.I., for guidance and to Prof. K. N. Kaul, F.L.S., for certain suggestions and keen interest in the progress of this work.

REFERENCES

Bhargava, H. R. .. "Contributions to the morphology of Boerhavia reparMa," d. Indian bet. Sac., 1932, 11, 303-26. Eichler, A.W. .. Blutendiagramme, 2, Leipzig, 1878. !nouye, R. . • "Anatomical studies in the vascular system of Mirabilis jalapa," Bet. Magazine, "Iokyo, 1956, 69, 554-59. Joshi, A. C. and Roe, V.S. "Vascular anatomy of the flowers of four Nyctaginaceae," dour. Ind. Bet. See., 1934, 13, 169-186. Metcalfe, C. R. and Chalk, L... Anatomy of the Dicotyledons, 1950, 2, London. Nair, N. C. and Nair, V.J. .. "Studies on the morphology of some l'qyctaginace~. I. Nodal anatomy of Borehavia," Proe. Ind. Aead. SoL, 1961, 54, 281-94. Schleiden, J. M. .. Principles of Scientific Botany, London, 1849. Sharma, H. P. .. "Morphological studies in the order Centrospermales,". Agra University Ph.D. T~,esis, 1958 (Unpublished).

EXPLANATION OF FIGURES Ftas. 1-18. Figs. 1-9. Showing nodal anatomy in Boerhavia repanda. Fig. 1. Diagram- matic representation of the vascular arrangement at a node. Figs. 2-9. Serial transverse sections of the stem passing through a node. Note branching of medullary bundles (A) and origin of inflorescence supply (I) from branches (a). Figs. 10-18. Showing nodal anatomy in Boerhavia diffusa. Fig. 10. Diagrammatic representation of the course of vascular bundles through successive nodes. Figs. 11-18. Serial transverse sections of the stem passing through a node. Mark origin of inflorescence supply (I) from the medullary bundle (u') alone and interconnection of the various medullary bundles. (A,,large medullary bundles ; a., branches of bundles A in B. repanda and smaller mcdullaD bundles in B. diffusa; a'., smaller medullary bundle providing inflorescence trace; B. large, axillary buds; b, smaller buds between B and the subtending leaf; F, inflorescence; I, inflorescence supply; L, Leaf supply; P, peripheral vascular ring.)

FIGs. 19-25. Showing nodal anatomy in Mirabitis jalapa. Fig. 19. Diagrammatic representation of the course of vascular bundles at a node. Figs. 20-25. Solial transverse sectiors B4 50 H.P. S I-/ARMA of the stem passing through a node. Note the fusion of bundles of the internaediate ring (S) with medullary bundles and leaf-trace bundles. (Symbols as previously explained.)

Fzos. 26-41. Showing nodal anatomy in Bougainvillea ~pectabilis. Fig. 26. Diagram- matic representation of the course of vascular bundles at successive nodes. Figs. 27-37. Serial transverse sections of the stem passing through a node. Mark the origin of vascular traces of leaf L 1 from medullary bundle (A) and leaf L2 from the bundle (At). (a, aj, bundles supplying the infloresc,~nce). Figs. 38 and 39. Showing branchivg in one of the axillary shoot. Fig. 40. Showing leaf arrangement (1-I1) at successive nodes. Fourth leaf (marked 4×) not shoran. Fig. 41. Showing arrangement of various axes at a node. (Symbols as explained earlier.)

FIOS. 42-63. Fig. 42. Diagrammatic representation of the floral arrangement in tl2e inflorescence of Boerhavia repanda. Figs. 43-47. Serial transx, ersc sectior, s of the inflorescence of B. repanda from base upward. Fig. 48. Diagrammatic representation of the floral arrange- mont in the inflorescence of Boethavia diffn~a. Yigs. 49-51. Serial transverse sections of the inflorescence of B. diffusa from base upward. Mark the successive origin of flowers (1-5). Alq, first floral axis of the inflorescence ; A, main flower ; B, lateral flower of A. Fig. 52. Diagram- matic representation of the bract arrangement in the "fewer" of Mirabilia jalapa. Fig. 53, Showing dichasial branching of the inflorescence atlower levels. Figs. 54-58. Serial transverse sections of the "flower" of M.jalapafrom base upward. Note the evanescent axillary supply (b). Fig. 59. Diagrammatic representation of the inflorescence of Bougainvillea spectabilis. Figs, 60-63. Serial transverse sections of the inflorescence of B. spectabilis from base upward. (br, bract; brl, bracteole; C, central flower; Fa ...Fs--flowers arising successively; X, missing flowers.)