37 2 Sahni .— On the Branching of the Zygopteridean Leaf. 
So far as Stauropteris is concerned, its supposed Edification parallele is 
clearly the result of Dr. Bertrand’s omission to take account of the 
‘ embedded trace ’. In Fig. 2 , A, the rectangular system of branching is 
diagrammatically shown. The numbers i, 2, 3, refer to the primary, 
secondary, and tertiary axes, and may be taken to correspond to the 
vascular strands of the leaf, pinna, and pinnule in the three types of 
Zygopterideae shown (B, C, D). The arrows indicate the planes of principal 
symmetry. In Metaclepsydropsis the tertiary strands, which at some 
distance from the base almost directly face the antero-posterior plane of the 
3 
2 
Q Stauropteris 
Fig. 2. 
leaf (as shown by the dotted arrows), are purposely drawn almost facing the 
right-left plane, in order to diagrammatize. In fact, if they are traced 
downwards they actually do tend to assume positions nearly facing each 
other (see Gordon, Figs. 37-40). It is probable that their position higher 
up the raches was partly responsible for the belief that they were pinna - 
traces directly facing the primary petiolar trace. In the case of Stauropteris , 
however, the orientation of the corresponding strands could be verified by 
other means, viz. the positions of the two main phloem-masses, which, 
according to Bertrand, invariably lie in the principal plane on each strand. 1 
1 I am not in a position to vouch for the correctness of the orientation of the tertiary traces as 
indicated in Fig. 2, D. It is possible that the arrows may have to be drawn as shown by the dotted 
lines. This would conform more clearly to the condition in M. duplex and other species. 
