172 BOTANICAL GAZETTE [MARCH 
reproduces sexually every year at approximately the same sea- 
son, while in other localities it is to be found continually, but 
never reproducing sexually. The chief factor which brings 
about this difference seems to be the relative permanency of the 
water, spores being produced on temporary ponds and no spores 
On permanent ones. - 
The heavy-walled resting spore is suited to endure unfavor- 
able conditions. When the water withdraws, the spores are left 
on the mud or even on dry soil, a condition which may be a 
necessary preparation for germination. The spores germinate 
early in the spring of the year following their maturity, that is, 
nearly a year after they have been shed. The water may remain 
long enough after the fruiting season for a period of vegetative 
multiplication to intervene, and thus many plants may be left to 
grow on the mud, If the mud remains very wet, there are pro- 
duced beautiful rosettes like fig. 2, formed of numerous slender 
branches that remain connected at the center of the rosette. 
As a rule, there seems to be little chance of survival for the 
stranded plants. From the under surface there is put -forth a 
dense mass of rhizoids which anchors the plant firmly to the 
soil. Soil contact causes the older ventral plates to wither, but 
new ones continue to be produced at the apex in the usual way, — 
though they cannot become prominent because the rhizoids pull 
the plant down close to the soil. If the water should return, 
these plants would be submerged, and, unable to float to the 
surface, would very likely perish, as most of the plants growing 
on the soil probably do. In special cases, however, the land 
plants have been able to endure the submergence, until by decay 
of the older portions the young tips of the branches are set free, 
when they rise to the surface and develop into the floating form 
again. By taking large healthy branches from the soil and pla 
cing them in water, it was found that only the extreme tip remains 
slightly above the water surface. The remainder extends vert 
cally into the water and soon decays, while the young be 
develops the usual floating form of the plant. 
If the body of water is permanent, the surface may be covered 
with small plants that multiply vegetatively throughout the seaso® 
