52 Davis . — The Fertilization of Batrachospermum . 
a branch one procarp followed another, each identical in 
appearance with its neighbour. In the case of B. monitiforme , 
the monoecious species, a very fair proportion of the tricho- 
gynes were free from antherozoids, perhaps because the quiet 
water in the jar prevented the filaments of the plants from 
rubbing together. Those procarps whose trichogynes lacked 
antherozoids never developed fruit, while neighbouring tricho- 
gynes with antherozoids fastened to them were attached to 
cystocarps in various stages of development, some with ripe 
spores. The evidence seemed almost conclusive that fusion 
of an antherozoid with the trichogyne was absolutely necessary 
for the production of fruit. As the reader proceeds, he will 
understand why it is desirable to dwell upon this point, even 
though it be what has always been considered a settled fact. 
The tissues of Batrachospermum may be most readily 
studied from crushed-out preparations, which are very easily 
made because of the flexible character of the filaments and 
the amount of mucilaginous matter in the frond. It has been 
the writer’s experience that absolute alcohol is the most 
satisfactory fixing agent, for it preserves the mucilage, which 
is very helpful in the further manipulation of the material. 
Chromic acid dissolves the mucilage. It is also possible that 
chromic acid may weaken the attachment of the antherozoids 
upon the trichogynes, and allow them to be more easily torn 
off in manipulation ; for it was in material fixed with this 
reagent that the writer found many specimens of cystocarps 
whose trichogynes were without these accompanying struc- 
tures. Of the many stains tried, the haematoxylin formulae 
gave the best results, and the most satisfactory of these were 
Mayer’s haemalum and acid haemalum, the latter being the 
more precise stain. Bohmer’s haematoxylin is also good. 
There is little choice between the common fixing agents, and 
absolute alcohol was employed for the reason before stated, 
that material killed with this fluid was more easily crushed 
out because of the mucilage contained in the frond. High 
powers of the microscope were necessary throughout the 
investigation, and the writer used the Zeiss 4 mm. apochro- 
