20 BOTANICAL GAZETTE [jury 
mate marginal cells on each side are devoted to the formation 
of sporangia, all of those of each sorus arising from one of these 
four sporangial marginal cells. The sori thus arise in right and 
left pairs, one above the other on each side, and are not terminal 
in origin, as described by Meunier, nor with two sori on the 
median plane, as indicated by Campbell. These sporangial 
marginal cells give rise in a way somewhat similar to that found 
in Marsilia, to the large number of sporangium mother cells of 
the sori, and are in the meantime surrounded by the more vigor- 
ous growth of the other portions of the ventral side of the cap- 
sule. By the more rapid growth at the base of the capsule on 
the ventral side, the openings of the soral canals thus formed are 
pushed around from a lateral position to become nearly terminal 
in the mature sporocarp. 
The macrosporangia and microsporangia are not derived 
from different marginal cells, as in Marsilia. The earliest evi-— — 
dence of differentiation found here is in the fact that the first — 
sporangia formed, most of them near the base of the sorus, seem 
to develop macrosporangia, while the upper and younger ones 
become microsporangia. Except in this matter of location, the 
two kinds of sporangia are just alike up to the formation of the i 
spore mother cells. ‘ae 
Sat. eae 
eae 
sori from each other. It seems to me that Meunier is right in 
saying that the development of this tissue here (as in Marsilia 
also) is sufficient warrant for calling it an indusium. But we 
cannot agree with Campbell in regarding these indusia as t 
inturned edges of leaflets enclosing the sori, since we have 
evidence that any structure homologous with the lamina 0c: ul 
in the capsule. : 
Of course, the whole question of homology is comp 
by the fact that the sporangia of the Marsiliaceze seem tt 
on the ventral surface of the leaf, But if we pass from f 
like Asplenium, with sporangia borne near the middle of 
