50 Davis . — The Fertilization of Batrachosper 7 num. 
had been tom off in the manipulation of the specimens. This 
interesting question of possible apogamy led the writer 
to try some experiments upon living plants that had best be 
considered at the outset. 
In nature, the filaments of the Batrachospernmm- plants, 
being attached to stones and other objects usually in running 
water, float out in the direction of the current and wave 
slightly to and fro with the varying movements of the stream. 
As the plants grow in tufts, the separate filaments necessarily 
touch and scrape against one another when their positions 
change in the flowing water: hence it seems quite possible that 
the antherozoids of one plant or filament might readily be 
brushed off upon the trichogynes of another as the branches 
move from side to side. It is difficult to understand how the 
antherozoids could be brought in such profusion and applied 
to the trichogynes by swiftly-moving water, and the above 
explanation of the process of fertilization appears very 
plausible to the author. 
To determine experimentally whether contact of anthero- 
zoids with trichogynes is absolutely necessary for the pro- 
duction of fruit, it is necessary to grow plants under such 
conditions that the possibility of fertilization either by direct 
contact of the filaments or by currents of water is removed. 
The normal conditions of environment, temperature, light, &c., 
must at the same time be strictly adhered to, in order that the 
experiment may be conclusive. Batrachospernmm Boryanum 
is a strictly dioecious species ; and one may frequently find 
plants of B. coerulescens which bear very few or no anthero- 
zoids : but this special form of B. moniliforme is monoecious. 
It is an easy matter to select female plants of B. Boryanum 
and B. coerulescens , and to clear the stone upon which they 
grow of all male plants. However, it is not easy to grow such 
female plants isolated in aquaria, because it is so difficult to 
imitate the normal surroundings of Batrachospermum- plants 
as regards the temperature of the water, for they frequently 
grow in ice-cold streams : the plants do not thrive when 
removed from their running brooks : But the writer believes 
