164 Campbell . — On the Development of 
sporangium, the remains of the tapetal nuclei (Fig. 36 n) 
may be seen occupying much the same position with reference 
to these that those of the microsporangium do to the mas- 
sulae. This, together with the similarity in the structure of 
the epispore of the macrospore, and the massulae, warrants 
the conclusion that the two are homologous structures. The 
threads attached to the epispore may morphologically as 
well as physiologically be compared to the glochidia. 
Sometimes, but not always, a cleft may be seen extending 
upward part way through the central conical mass, but in no 
cases is there such an open canal as described and figured by 
Berggren 1 for A, caroliniana. 
The Microsporangia. 
In the male sorus, as we have already seen, the apical cell 
of the young rudiment does not form a sporangium, but gives 
rise to a central columella or placenta, from which the 
microsporangia arise laterally, while the end projects as 
a cylindrical body (Fig. 22 coif This latter was observed 
by Meyen 2 , but Strasburger seems for some reason to have 
overlooked it. I found it in all my sections of the male sorus. 
As in the female sorus, the indusium is two cells in thickness, 
but the cells have their walls more uniformly thickened, and 
the inner layer is not compressed as in the female sorus ; as 
in the latter, the opening at the top becomes completely 
closed, and the cells about it are thicker walled than the 
lower cells, and reddish brown, as in the upper cells of the 
indusium of the female sporocarp. Like that, too, the top 
is pointed, but the point is short and abrupt, and the body of 
the sporocarp is globular. They are more than twice as 
large as the female sporocarp. Both sorts of sporocarp have 
a very short stalk, into which a fibrovascular bundle extends 
for a short distance. 
The development of the microsporangium corresponds 
closely to that of the macrosporangium, but differs in some 
1 loc. cit. p. 1 ; also, Fig. i. 
2 See Strasburger, loc. cit. p. 57. 
