1 66 Campbell.-— On the Development of 
(Fig. 24 n), indicates that, like the appendages of the 
macrospore, these too are formed in part, at least, by the 
activity of the tapetal nuclei. In A. filicnloides the glochidia 
are undivided, except occasionally toward the tip, where one 
or two septa may sometimes be detected. 
When the sporocarp of Azolla is compared with that of 
the other Hydropterideae, its nearest approach is found in 
Salvinia , with which it agrees closely in its origin and 
structure. Each sporocarp is a single sorus with a cup-shaped, 
completely closed indusium, while in the Marsiliaceae the 
sporocarp represents a whole leaf-segment with several sori. 
Among the homosporous Ferns, some of the Cyatheaceae and 
Hymenophyllaceae (especially T richomanes), show very marked 
resemblance to the Salviniaceae in the position and form of 
the indusium. 
Germination of the Microspores. 
The study of the germinating spores offers great difficulties, 
as they are completely imbedded in the massulae, and 
cannot be freed in the living state. Belajeff 1 , who has recently 
published some observations upon the male prothallium of 
A. filicnloides, treated the massulae with chromic acid which 
rendered them brittle enough to be broken in fragments, thus 
setting free the prothallium. My own observations were 
made mostly from sections. As the massulae adhere to the 
macrospores, in making sections of the latter, the massulae, 
with their enclosed spores, were also sectioned. Of course 
in this way it is impossible to regulate the direction in 
which the sections are made, but enough straight sections 
were obtained to give a clear idea of the development of 
the antheridium. In the material used by me, only a small 
percentage of the microspores seemed perfectly developed, 
and in consequence, the number of male prothallia found was 
very small compared to the number of massulae sectioned. 
As the germinating spores are completely buried in the 
massula, it is very difficult to judge of the state of develop- 
1 loc. cit. 
