570 
MR. F. O. BOWER ON THE COMPARATIVE MORPHOLOGY OF THE 
Welwitschia; in other cases by differences in the distribution of growth in tranverse 
and longitudinal directions, a different conformation may be acquired at different 
parts : thus a basal part or hypopodium may be recognised, which coincides with 
Eichler’s “ blattgrund ” : a median, elongated part, the mesopodium, which coincides 
with the petiole : and thirdly, an apical part, the epipodium .* 
It will be necessary to say a few words upon the third part of the phyllopodium, 
in order to show how it differs from the “ oberblatt ” of Eichler, this beinsr the 
essential point in which his method of treatment differs from that which I am 
endeavouring to establish. Under the term “ oberblatt.” Eichler and Goebel include 
the whole of the upper part of the leaf whether branched or unbranched : supposing 
the leaf to be unbranclied, the term “oberblatt ” will include precisely the same part 
of the leaf as I wish to express by the term “ epipodium,” But in the case of branched 
leaves, while the term “ oberblatt ” will include the whole of the upper part of the 
leaf with its branches , in fact a whole branch-system, I should include under the term 
epipodium only the upper part of the phyllopodium with its wings, and exclusive of 
its branches of higher order. The difference of application of the terms may seem at 
first sight small, but beneath it lies an important difference of morphological method. 
By Eichler the leaf is treated as one member, which may branch in its upper part; 
under the method which I propose it is treated throughout as a potential branch- 
system ; under the former method a sharp distinction is drawn between the basal part 
of the leaf, and the upper part which may or may not branch ; under the latter the 
distinction is between the podium, and the branches (if any) which it bears. 
It seemed to me to be important to test the validity of my views as to the mode of 
procedure in studying the morphology of the shoot by a series of observations on those 
plants of the vascular series! which are universally allowed to be lowest in the scale, 
and this comparative study of the leaf seemed especially necessary, since it has been 
much neglected by those to whom we owe the chief advances in our knowledge of leaf- 
development. I had previously been engaged on the development of the leaves in the 
Cycadacece and Gnetacece, and thus a good opportunity was offered of working in the 
results obtained in those groups with those obtained by other writers and by myself 
in the vascular Cryptogams, so as to arrive at a comparative view of the development 
of the leaf in the whole series. It may be stated that the result of this comparative 
* Mj reasons for introducing a new terminology are two. First, it is desirable to dispel as far as 
possible the idea upon which so much stress is laid by Eichler, that there is an important difference 
between the “ blattgrund,” and “ oberblatt ” (7.c., p. 25, “ wesentlich von einander verschiedene Theile ”): 
this may best be done by dropping his terms ; secondly, while rejecting the general term “ oberblatt ” 
as expressing an idea which is not in accord with morphological method as applied to the axis, it is 
desirable to observe uniformity in the terminology. 
t I purposely leave out of account the foliar Muscinece, though these are so often used in comparison 
with vascular plants. It is often forgotten, while comparing' the vegetative organs of Muscinece with 
those of the vascular plants, that the structures compared are not homologous, but at best only analogous 
developments. 
