256 THE JOURNAL OF INDIAN BOTANY.
The leaf-stalk is dorsiventral in its organisation, markedly so in
its upper part where it has a distinct groove on its adaxial side. The number of vascular bundles varies from nine to eleven, those nearest the groove being the smallest. (Fig. 3)
The basal part of the tendril is radial in section, the number of bundles various from sis at the lower to ten in the upper part, and they are as a rule arranged in one ring. There is absolutely no trace of a ventral groove as is present in the petiole. (Fig. 4)
Both the branches of the tendril show a dorsiventral structure with a distinct groove on the apparently upper surface. The vascular bundles are five in number in the form of an arc open above as seen in a transverse section. (Fig. 5)
The vascular connections at the node are as follows : — The traces from the tendril, the vegetative bud and the flower-stalk all pass through the cortex and join the bundles of the inner ring. The leaf-stalk sends three traces into the cortex. Of these, one (median) passes down the internode below without anastomosing with any bundle at the node ; the two lateral traces join the two adjacent bundles of the outer ring, each with the one on its own side. One bundle of the inner ring, while coming from the upper internode, gradually decreases in size and ultimately ends blindly immediately above the node or just reaches it. The bundles of the inner ring anastomose at the node and this ring receives a bundle from the outer ring also to take the place of the one that has just ceased at each node. Thus at every node one bundle of the inner ring stops and a bundle from the outer ring joins the inner ring to take its place 1 while the place of the latter is taken by the median leaf-trace which passes down the lower internode without anastomosing. The gradual decrease in size of one of the bundles of the inner ring at each internode, as described above, is the cause of the dorsiventrality of the arrangement of the vascular bundles common in the family. (3)
It is clear from the above description that the bundles of the outer ring are really continuations of the leaf-traces, while the bundles of the inner ring are mainly cauline.
Lagenaria vulgaris,
The organs at the node beginning from the left are, a branched tendril with five arms very close to each other, a bud and a flower. The glandular organ is missing.
The vascular structure of the stem and the leaf-stalk is in general the same as in Benincasa cerifera.
1 This now inner bundle is not, however, a direct continuation of the outer bundle.
