Azolla filiculoides , Lam . 163 
sporangium completely, and that the latter is in close contact 
with the indusium except at the top, where there is a space 
between filled with the resting cells of the Anabaena (n). 
The sporangium-wall at this point (Fig. 35 sp.) is perfectly 
plain, but the cells have collapsed so that the separate cells 
are not very easily distinguishable. Near the base of the 
sporangium, however, they may generally be very easily seen, 
especially when, as often happens in sectioning, the wall is 
pulled away from the indusium. (See Fig. 38 sp.). 
The curious episporic appendages of the macrospore have 
been frequently described, but the homologies of the parts 
have not been entirely understood. The ripe spore is per- 
fectly globular and surrounded by a firm yellowish exospore, 
which appears almost perfectly homogeneous in section. 
Upon this is deposited a thick epispore of most peculiar 
form. This is covered with cylindrical papillae from the 
top of which numerous curious threadlike filaments extend. 
In section the epispore shows two distinct portions, an inner 
mass resembling exactly the substance of the massulae, and 
a denser part that covers the outside except the tips of the 
papillae. This outer part is solid and nearly homogeneous, 
in places densely granular. The epispore covering the top 
of the spore is developed in a most extraordinary manner. 
It consists here of four parts; a central conical part, and 
three somewhat pear-shaped masses that are partly sunk in 
shallow cavities in the sides of the central portion. To these 
Strasburger applied the name ‘ Schwimmapparat,’ supposing 
them to be filled with air, and to thus raise the spore to the 
surface of the water. Repeated experiments with perfectly 
ripe spores, both before and after they had been freed from 
the indusium, resulted invariably in the spores sinking 
immediately, as was the case with the ripe massulae. This 
being true, the name must be abandoned as misleading. 
From the conical mass, as well as from near the apex of the 
others, the filaments, like those growing from the papillae 
of the lower part of the spore, are produced in great numbers. 
In the spaces between the masses, even in the full-grown 
