Boodle.—Anatomy of the Hymenophylloceae . 485 
thus placed that also had prothalli resting on them, the pro- 
thalli agreeing well in appearance with those produced by 
germination of spores in situ. The evidence cannot be called 
conclusive that the prothalli and young sporophytes belonged 
to T. hymenophylloides , but it is very nearly so. The reason 
for which these are mentioned is that the first two leaves were 
not filmy, but had numerous intercellular spaces and stomata. 
Unfortunately none of the sporophytes had advanced further 
to form filmy leaves. Some ‘ seedlings ’ of Todea Fraseri , 
Hook, and Grev., and T. hymenophylloides supplied by Messrs. 
Backhouse, did not agree with the above, their first leaves 
being entirely filmy. This would make one doubt the identity 
of the other seedlings, but it is quite possible that when the 
prothalli and young sporophytes are grown under normal 
conditions, the first leaves are filmy, but that when grown 
under the abnormal conditions of the first case, the first 
leaves might show signs of reversion. 
Some of the leaves of Asplenium resectum , the other filmy 
plant examined, possessed evident abortive stomata. The 
mother-cell of the stoma had in some cases remained un¬ 
divided (as in Fig. 45, m.c.) and in other cases it had under¬ 
gone division into two cells, resembling guard-cells, but of 
course destitute of a pore (Fig. 44, g). The lamina in this 
species is mostly two cells thick. This species is further 
interesting because some specimens are filmy, while others 
have leaves with abundant stomata and intercellular spaces. 
The filmy form is separated as var. udum } Clark, so that the 
filmy character is here not even of specific value. 
For Asplenium resectum it is clear that the filmy habit is 
a modification of the normal type of leaf, as evidenced by the 
functionless rudiments of stomata. In Todea , accepting the 
seedlings mentioned as belonging to T. hymenophylloides , the 
same appears to be the case ; but in the Hymenophyllaceae 
similar evidence is at present wanting as to whether the filmy 
habit is primitive or reduced. As, however, the anatomy 
of the stem appears to point to a series of reduction, it is 
probable that the filmy habit is secondary and not primitive. 
