1906] LEWIS—DEVELOPMENT OF RICCIA BIT 
supplied with sufficient moisture. In some cases the mud became 
so dry and hard that the plants were killed, but whenever they were 
sheltered by a stone or other object, or were growing on the sides 
of holes, such as cattle tracks, they grew well. 
In October all but the youngest and most crowded plants showed 
the typical Riccia lutescens form. At this time young antheridia 
were found. Material was now collected and fixed from time to 
time for the purpose of studying the development of the sexual 
organs. In very few cases were archegonia found in plants collected 
in autumn. A few young stages were found in plants collected 
late in November, at which time the older antheridia were almost 
mature. No further development took place out of doors until 
spring, because the plants became covered with snow, or with water 
by the filling up of the ponds, and remained so until April. A 
quantity of the plants were kept growing on the soil in the green- 
house through the winter, and developed mature sexual organs 
long before spring. Plants taken from under water in March, just 
as the ice was going out of the ponds, showed exactly the same form 
_ as in November, and little or no further development had taken 
place. So it seems that the development depends to some extent 
on temperature, and might be expected to vary with different con- 
ditions of climate. A warm winter, in which some growth might 
take place, would in all probability hasten the development of the 
sexual organs. Another point of interest is that the submerged 
plants did not seem to have been injured. 
A quantity of material still attached to the soil was taken from 
under water late in March, and was kept growing in shallow pans 
in the laboratory so that it could be kept supplied with a sufficient 
quantity of water for growth but not enough to flood the plants. 
This was done in order to determine whether the plants would con- 
tinue the development of sexual organs and fruit in the same way 
when supplied with a limited amount of water and growing on the 
soil, as when supplied with a large amount of water which would 
tend to cause them to break loose and float. It was found that the 
plants growing on the soil did produce fruit abundantly and at 
the same time as those growing under natural conditions. The 
archegonia begin to develop in April in the same thalli which have 
