LEAF' IN THE VASCULAR CRYPTOGAMS AND GYMNOSPERMS. 
569 
Ruscus, and Phyllocladus , one axis is frequently cylindrical below, and gradually 
more flattened above, yet no morphologist would lay any stress upon the distinction 
between the flattened part and the part which is cylindrical; both are regarded as parts 
of one and the same axis, though the transverse growth is not uniform throughout. It 
was, however, chiefly on the ground of an external conformation due to an unequal 
distribution of transverse growth, coupled with a “stationary” character,"" that the dis¬ 
tinction between foliar base and upper leaf was based ; and this is not sufficient ground 
for distinguishing two categories which, as I have shown above, are not morphological! y 
coordinate. If the shoot is to be treated uniformly and consistently, the treatment 
of the leaf must be modified.t 
Instead of drawing the distinction, in the first instance, in leaves whether branched 
or unbranched, between the foliar base and the upper leaf, I propose to treat the whole 
leaf, from apex to base, consistently as a podium, or form of axis, which may or may 
not branch, and which may develop in different ways at different points. It will be 
necessary to define this podium by the use of a distinct term, which shall include not 
only a part of it, but the whole of it from apex to base, exclusive only of its branches. t 
Various words have been used by different authors, who have felt the necessity of 
defining this podium : thus “ racliis ” has been used, but this term has already another 
distinct application; the old term “midrib ” has also been used, but this is unsatisfac¬ 
tory, since it implies that it is the rib which is at the middle of something, and this is not 
always the case, nor is it that character of the structure which it is desired to describe. 
I therefore propose the term phyllopodium to express the whole of the main axis of 
the leaf, exclusive of its branches, the word being similar in composition to the terms 
“ sympodium,” and “ monopodium.” 
As is also the case with stem structures, the phyllopodium is capable of very various 
development. In the simplest examples it remains unbranched, and it may then 
develop (1) in a cylindrical manner, as in Pilularia; or (2) it may appear as a 
flattened structure without wings or midrib, as in Welwitschia and many Monocoty¬ 
ledons ; or (3) it may be simply winged, through part or the whole of its length, as in 
Gnetum. In other cases the phyllopodium may branch, the branches being produced 
in acropetal or basipetal order: these may appear in the mature leaf as teeth at the 
margins of the wings, or as distinct pinnae, which may themselves develop in various 
ways, and again branch, forming pinnules, and so on to higher orders of ramification. 
As will be pointed out more at length at the close of this paper, the phyllo¬ 
podium may develop uniformly throughout its length, as is the case in Pilularia and 
* Eichler, lx., p. 7. Goebel, Bot. Zeit., 1880, p. 759. 
f Eichler even goes so far as to argue (lx., p. 24), in answer to the opinion of Mercklin and others, 
who regarded stipules as basal pinnae, that because the foliar base and upper leaf differ radically one 
from another, therefore members borne by them are not morphologically equivalent. 
t Of course no sharp line can be drawn between its branches and itself, just as it is impossible to 
define accurately the limit between stem and leaf. 
MDCCCLXXXIV. 4 D 
