Notes . 
IOI 
sion of certain cells of the potential archesporium into sterile tissue ; 
the unavoidable conclusion already drawn by other writers for this 
and other cases, is that these septate anthers are derived from those 
of the ordinary quadrilocular type, and the process of septation thus 
illustrated is essentially similar to that described for the Lycopodineae 
in my previous paper. We thus see that septation of sporangia has 
actually occurred , and that it is a rather ivide-spread phenomenon in 
Angiosperms. It will therefore be merely a question of probability 
whether, and how far, it has also occurred in lower forms, and whether 
it is by septation that those synangia were produced, which are so 
marked a feature in certain Pteridophyta. 
The argument from developmental evidence is comparatively 
simple where, as in the Angiosperms, the meristems are distinctly 
stratified, and the archesporium is a definite layer, ultimately hypo- 
dermal in origin ; but in applying a similar argument to the Pteri- 
dophyta, in which the meristems are not clearly stratified, it is less 
easy to arrive at a conclusion. The principle is to be laid down 
that the study of the sporangia or sy?iangia of a plant is to he carried 
out in the light of a knowledge of the segmentation of its apical meristems. 
The sporangia are parts of the plant-body, and their segmentations 
do not differ essentially from those of the meristems of the other 
parts of the plants on which they occur. Where the meristems are 
stratified, as in Angiosperms, a clearly stratified structure of the 
sporangia is commonly found ; where, as in the Pteridophyta, the 
meristems are not stratified, it would be plainly unreasonable to 
expect a stratified structure of the sporangia, and such structure is 
not found. Accordingly, in using developmental evidence in solving 
the question whether synangia in Pteridophytes resulted from septa- 
tion, the existence of a continuous hypodermal archesporium cannot 
reasonably be demanded as evidence of septation, though of course 
it may occur, as indeed it does in Isoetes ; it is, however, to be 
remembered that in this plant the meristems are more clearly stratified 
than in most Pteridophyta. 
The considerations thus briefly epitomized are a necessary prelude 
to the comparative study of the Ophioglossaceae. In my preliminary 
statement (Roy. Soc. Proc., Vol. 1, p. 265) I have described, chiefly 
from examination of Ophioglossum pendulum , a continuous hypodermal 
band as the potential archesporium, which subsequently was differ- 
entiated into sporogenous groups and septa; such a band appears 
H 3 
