4 
Birbal Sahni. 
each stolon bears only one crown of leaves), in Nephrolepis the 
stolon has extensive powers of branching. The apex of the stolon 
does not itself produce a leafy crown, but during its continued 
growth produces a large number of secondary growing points, many 
of which sprout into “ lateral plants ” 1 while the rest of them 
remain dormant. In view of the enormous length of the stolons, 
which ensures a corresponding increase in the number of lateral 
plants, and in the epiphytic habit of the latter, N. volubilis would 
seem to represent a further stage in the specialization of the filicinean 
branch. 
Turning now to the question from the point of view of the 
vascular anatomy, we find a series more or less parallel to the one 
we have based upon the external features. For our comparison we 
shall refer to Fig. 1, p. 5 which represents in a purely diagrammatic 
way the vascular relations of the branch to the stock in a number 
of Ferns whose mature structure ranges from protostely to an 
advanced type of dictyostely. In the figure the branches are 
supposed to have come off in all cases at right angles to the main 
axis, so that they can be drawn as seen in longitudinal section while 
the main axis is seen in transverse section. In the branch the 
protostelic portion is shown as a single black band arising from the 
main axis; the solenostelic portion is shown as two bands which 
are parallel except towards their proximal ends, where the soleno- 
stele is seen to contract. In the solenostelic portions (whether of 
the main axis or of the branch), the leaf-gaps are not indicated, for 
the sake of better distinction from the reticulate portions, which 
are represented by interrupted bands. The leaf-traces have been 
omitted altogether, and no attempt has been made to draw the 
diagrams to scale. 
Some of the diagrams would require further explanation in 
view of the facts that the branch very frequently arises in close 
association with a leaf, in an “ axillary ” or “ infra-axillary ” position, 
and that its vascular supply appears actually to originate from the 
trace of the related leaf, as in some Hymenophyllaceae, species of 
Zygopteris, in Cibotium, Plagiogyria, Lophosoria, Metaxyn, Cheiro- 
pleuria and Botrychium Lunaria. Without entering here into the 
question of the morphology of the organ in Zygopteris termed by 
Dr. Scott the “ undivided trace,” it may be stated that the view here 
adopted regards the branch as arising from the main axis, but with 
’ Thus with respect to the mother plant the lateral plants are usually 
branches of the second order. If, however, the apex of the main stolon is 
arrested, it is replaced by one of the neighbouring secondary growing points. 
