198 BOTANICAL GAZETTE [ SEPTEMBER 
into single cells did not occur. The plants in the greenhouse 
were not, however, especially dry. 
IO. PHASCUM CUSPIDATUM. 
The leaves of Phascum produced protonemata with great 
readiness and in less time than any other species investigated. 
Cultures were made for both light and dark, part of the leaves 
in each case being dorsal side and part being ventral side up. 
At the end of five days both protonemata and buds had been 
produced in the light, and a careful examination showed that the - 
majority of the growths originated from the ventral side of the 
leaf in the region of the costa, without reference to the position 
which the leaves had occupied in the culture. Occasionally a 
protonema originated from the leaf cells removed from the 
region of the costa, and now from the contact side and now 
from the free side of the leaf. Occasionally some of the cells 
from the region of the base gave rise to distinct rhizoids which 
showed no tendency to produce protonemal branches, but 
remained distinctly rhizoidal in nature even in the light. The 
branching of the protonemata in the light was not very profuse. 
while in those which remained in the dark all the time, the 
branching was suppressed to a considerable extent, and the. 
walls very soon turned brown. No buds were formed in the 
dark cultures, while the cultures in the light had plenty of buds 
at the end of five days. 
When the lateral halves of the leaves were separated from 
the costa, they also gave rise to numerous protonemata, show- 
ing that in the whole leaf the ability of regeneration was 
present, but that the supply of food material was contributed 
to the cells of the costal region, which produced protone- 
mata with greater ease. It has already been stated that the 
majority of protonema production in the whole leaves was 
from the ventral leaf surface in the region of the costa. Cross 
sections of the leaves showed that the cells occupying the costal 
region on the ventral side were thinner walled than the remainder 
of the leaf cells, hence they produced protonema more readily- 
