90 G wynne- Vaughan. — Observations on the 
are very irregular in shape, with beautifully undulated out- 
lines. There are numerous stomata on the under-surface 
of the leaf, which are overtopped by the neighbouring epi- 
dermal cells in such a manner that the outer walls of the 
guard-cells are at the level of the inner walls of the cells 
of the general epidermis (Fig. 12). The external longitudinal 
ridges of the guard-cells are well developed and highly 
cutinized ; but the internal are absent, although the corre- 
sponding region of the wall becomes cutinized. I was unable 
to ascertain the way in which the stomata were developed 
owing to absence of a sufficiently young leaf. 
General Considerations. 
In seeking to determine relationships between Loxsoma 
and the other Ferns, using the anatomy as a guide, I venture 
to regard the solenostely of the stem and the peculiar horse- 
shoe shape of the petiolar meristele as characters of primary 
importance, and of considerable reliability. Judging from 
this point of view, it would appear that the nearest allies to 
Loxsoma are to be sought for among those more primitive 
Cyatheaceae and Polypodiaceae that are included, together 
with Loxsoma itself, in Bower’s proposed sub-order Gradatae x . 
More especially is it related to certain species of Dennstaedtia 
and Microlepia (given by Hooker as sections of the genera 
Dicksonia and Davallia respectively). It is difficult to be 
more precise upon this point at present, because neither of 
these two sections, as at present constituted, are altogether 
homogeneous in their anatomical aspect ; at least, so far as 
I have been hitherto able to ascertain. Nevertheless, the 
majority possess a typically solenostelic vascular system, and 
a hippocrepiform petiolar meristele, just as in Loxsoma. As 
regards minor detail, in most of the species of both sections 
the protoxylems in the petiole are bordered by cavity- 
parenchyma, and elements resembling the sclerosed sieve-tubes 
1 The Morphology of Spore-producing Members; iv. The Leptosporangiate Ferns 
(loc. cit.). 
