1898 | REGENERATION AS EXHIBITED BY MOSSES 185 
exposure to light must have contained a considerable supply of 
plastic material, which was used in continued growth rather 
than in the formation of leafy shoots. No structures at all 
resembling rhizoids were produced, and at the end of the experi- 
ment the protonemal filaments were beginning to die from lack 
of food material. From these results it will be seen that in the 
case of Bryum capillare a continued exposure to light is neces- 
sary for the production of buds, 
In order to determine whether the cells removed from the 
basal region of the leaf were able to produce protonemata as 
readily as those of the base, a series of cultures was made in 
which the leaves were cut transversely through the middle, and 
both basal and apical portions retained in culture. The basal 
half of the leaf produced protonemata from both the proximal 
and distal ends, but only rarely from the cells occupying the 
interior. The apical half of the leaf also produced protonemata 
from the cells next the cut base. (figs. 77, 78, 79.) Another 
series of cultures was made in which the leaves were cut length- 
wise, and these showed protonema production from the base and 
also from the cut margins. These experiments then show that 
almost any cell of the leaf may grow out into a protonema, but 
that in the cells with one side next the margin, the tendency to 
form protonemata is greater than in those cells which are sur- 
rounded on all four sides by others. 
The experiments with whole plants placed under like condi- 
tions as the separated leaves, showed no protonema production 
whatever from the leaves, and when the tips of the leaves in 
whole plants were cut away, even then the leaves formed no 
protonemata. Thus nothing more or less than a complete sepa- 
ration of the leaves from the stem would suffice to call forth the 
power of the leaf cells to grow out into protonema filaments. 
Experiments with leaves grown in blue and red light brought 
a different result from that found in the case of the Mnium 
leaves. The leaves in the red light produced buds, apparently 
with as great readiness as in normal illumination, while in the 
blue light no buds whatever were formed. When we reflect that 
