i8 
Birbal Sahni. 
leaf, while in other cases it may apparently arise from the petiole 
of the related leaf, some distance from its base, either on the adaxial 
or the abaxial face. 
Moreover, although in a general way the relative positions are 
fairly constant for each group taken by itself, this constancy tends 
to be discounted when we consider the vascular relations of the 
branch and leaf. In those Hymenophyllacese in which “ axillary 
branches” are generally found it sometimes happens that the 
branch-trace is inserted on the main stele independently of the 
leaf-trace. Boodle 1 records one such case in Trichomanes radicans, 
and I have myself seen other cases in herbarium specimens. 
Mettenius 2 also draws attention to the varying position of the 
branch bud in the Hymenophyllacese. We have already referred 
to Professor Lang’s statement (see p. 1) that the branch-trace in 
Helminthostachys zeylanica is inserted directly on the main axis, 
some distance in front of the trace of the subtending leaf. In the 
closely allied species Botvychium Lunaria , however, the same 
author found that whereas usually the chief vascular connexion 
of the branch was with the adaxial face of the leaf-trace, in some 
cases the attachment was deeper in the axil and more closely 
related to the stele of the main rhizome. Within the Zygopterideae 
also we meet both with “axillary branches” having a vascular 
connexion with the trace of the subtending leaf, and with branches 
having their steles directly inserted on that of the main axis. 
Nor do we find that the numerical relation of one branch to one 
leaf is obligatory, more than one branch to a leaf having been 
recorded not only in several species of Hypolepis, but also in 
Cyathea mexicana, Dicksonici ( Cibotium ) Barometz , Polypodium 
grandiens, Cystopteris montana and other Ferns. 
Finally, considering the Ferns hitherto unmentioned we cannot 
detect in the great majority of them any relation whatever between 
the positions of branch and leaf. 
Thus if we view the Ferns as a whole it may be said that the 
branch does not hold any regular position with respect to the leaf; 
and the question arises whether the primitive condition was that in 
which leaf and branch were separate, or that in which they were 
produced in relation to each other. From his detailed study of 
Botvychium Lunaria and Helminthostachys zeylanica Professor 
Lang has concluded that the regular presence of axillary buds in 
these species is in favour of this relation being “ part of the 
1 Boodle, Annals of Botany, 1900, p. 473. 
* Mettenius, Abhandlungen der Kgl. Sachs. Ges., 1861. Ueber Seiten- 
Knospen bei Farnen, p. 615. 
