LEAF IN THE VASCULAR CRYPTOGAMS AND GYMNOSPERMS. 
CO!) 
from the Leptosporangiate Ferns, through the Osmundacece and Marattiacece to the 
Cycadacece, and there is no apparent objection on other grounds to thinking that these 
plants constitute a natural series ; in other words, that they indicate, at least roughly, 
a line of natural descent. If this be so we are confronted by a remarkable fact. It 
has been repeatedly insisted upon that the characters of the vegetative organs of 
Angiopteris approach very closely to those of certain Cycadacece. Yet between the two 
there is all the difference in the reproductive organs between the characteristic free 
prothallus and antherozoid of the Vascular Cryptogams, and the endosperm and pollen- 
tube of the Gymnosperms. This is one of the most striking examples in the vegetable 
kingdom of the non-parallelism in progress of the vegetative and of the reproductive 
organs : here while there is comparatively little progress in the vegetative organs 
from the Marattiacece to the Cycadacece, the sexual reproduction shows that great 
advance from the process characteristic of the vascular Cryptogams to that typical of 
the higher plants. The converse of this non-parallelism is also to be found at a 
different point in the vegetable kingdom, viz. : a persistence of the reproductive 
characters, while a great advance is made in the differentiation of the vegetative organs ; 
for example, between the Muscinece and the Filicinece there is all the difference 
in the differentiation of the vegetative organs of the sporophore, between a cellular 
structure without axis and leaf, and the simplest form of Fern plant; but meanwhile 
the sexual processes remained unaltered, there being no fundamental difference 
between the archegonium and the antherozoid in the Muscinece and the similar 
organs in Me Filicinece. Other examples might be brought forward of ti ns non-paral¬ 
lelism, but the two converse cases named are the most prominent in the vegetable 
kingdom. 
This paper has hitherto dealt for the most part with comparatively large and com¬ 
plicated leaves ; a word must now be said on the leaves of simpler organisation found 
among the Vascular Cryptogams and on the application of the method of treatment 
which I have proposed to them also. Some of the simpler forms of leaf may show little 
preponderance of growth in any given direction; this is the case in Azolla and 
Selaginella. To such leaves the application of the term phyllopodium is obviously 
unnecessary and unsuitable. In other cases the leaf may be of very simple organisa¬ 
tion, but still show a distinct preponderance of growth in a given direction, as in 
Pilularia , Lycopodium, many Coniferce and Gnetacece, and to a slight degree Salvinia . 
Here we may recognise a simple unbranched phyllopodium, which may be winged 
(eg., Gnetum, &c.), or cylindrical ( Pilularia ), or flattened ( Wehvitschia ). If such a 
leaf were to show the characteristic differentiation of those parts, we might dis¬ 
tinguish them as the hypo-, meso-, and epi-podium ; thus, for instance, in Isoetes, in 
which, as pointed out by Goebel (Hot. Zeit., 1880, p. 785), the basal part (hypo- 
approaches the Hijmennpliyllacece in this character, though its sporangium is similar to that of other 
Osmundacece. 
4 I 
MDCCCLXXXT V. 
