1904] WYLIE: ELODEA CANADENSIS II 
ends. As will bé seen later, there is reason for believing the 
male cells of Elodea make the greater part of the journey 
through the pollen tube still hitched together in this tandem 
fashion. 
During their continuance in the pollen grain the male struc- 
tures clearly reveal their morphology as cells. About the 
nucleus, which usually shows a nucleolus, there is an extensive 
mass of cytoplasm differing considerably from the contents of 
the spore, and all clearly invested by a limiting membrane. It 
was observed that one or two more deeply staining bodies 
usually lie outside the nucleus along the median line of the cell 
( figs. 64,65); if two of these are present, one lies at each side 
of the nucleus, though at varying distances from it. 
“PHENOMENA OF POLLINATION. 
While the general mode of pollination in Elodea is well 
known, the details, which seem never to have been published, 
- are of such interest as to merit a brief description. 
The staminate flowers are borne entirely beneath the surface of 
the water, and these, as is well known, break off and rise to the sur- 
face, there shedding the pollen. It is probable that with the ripen- 
ing of the sporangia, in the still submerged flower, gases given off 
by the plant fill the spaces about the spores as well as any other 
cavities developed in the flower. At maturity a bubble of oxy- 
gen forms at the tip of the flower, and with its enlargement the 
sepals open slightly. At this time, looking down into the flower 
one can see that the sporangia have opened, and that many of 
the spores have been shed into the central space. The oxygen 
bubble may finally become nearly as large as the flower, and, 
when conditions are proper, the buoyancy of the enclosed 
gas, aided by the low specific gravity of the flower itself, 
overcomes the weakened attachment, and the flower darts to the 
surface. Upon reaching the surface the bubble disappears, the 
sepals snap back quickly, and in their recurved position form 
three boat-like floats which support the sporangia above the 
water; these catch the breeze and the flower sails away. While 
such float devices for the staminate flower are thought to be of 
great importance in the pollination of Vallisneria, it is doubtful 
