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 medul- lary 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 them- selves 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 medul- lary 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.