1906] - LEWIS—DEVELOPMENT OF RICCIA It3 
which were outgrowths from the growing points of the older plants. 
The cattle tracks serve a good purpose, as the young delicate plants 
are shaded and protected to some extent during the dry season. 
Two forms of the thallus are produced by the different methods of 
propagation. In the one case the thallus after it becomes attached 
to the soil continues its growth, branches and forms a rosette, while 
in the other case the thallus is injured, and very delicate forms are 
produced. When large numbers of the floating thalli are deposited 
near together and are then injured, we find the irregular clusters 
of plants which have been described in the first paragraph. 
The thallus of this plant during the floating period bears such 
a striking resemblance to Ricciocarpus natans that one is led to the 
conclusion that Riccia lutescens is only a ground form of Ricciocar pus 
natans. Since the beginning of this study and after it was well 
under way, a paper was published by GARBER (11) which dealt. 
‘with the life history of Ricciocarpus natans. Several points in the 
biology of the plant as given by GARBER differ from those found 
to obtain at Ithaca, and since the structure of the thallus as well 
as the embryology is conclusive proof that the two forms are the 
Same species, it seems proper to call attention to these differences 
and then to give briefly the embryology before taking up the other 
phases of the study. 
The greatest difference in our observations lies in the relation 
of the supply of water to sexual reproduction. GARBER states that 
Ricciocarpus natans as it grows at Chicago spends its entire life, 
from the germination of the spore to the production of spores, in 
the floating state, and that the occasional fruiting plants found 
upon the soil in summer are plants in which the sexual organs devel- 
oped and the sporophytes began their development while the plants 
were floating. He observed no case in which sexual organs were 
produced on plants growing upon the soil and states that Ricciocar pus 
natans has not yet acquired the power to reproduce sexually when 
growing upon the soil. The sexual organs develop in April. 
The plants at Ithaca, however, spend the greater part of their 
life upon the soil and only float upon the water for a few weeks at 
the fruiting period. The sexual organs begin to develop in autumn 
while the plants are on the soil and plants kept on the soil and sup- 
