204 BOTANICAL GAZETTE | SEPTEMBER 
piece of flowerpot until a considerable size and vigor was 
attained, and then placed in the dark. At the end of two, weeks 
no sign of rhizoids was detected. The growth had, however, 
been considerable from the supply of food material which had 
been produced in the light. 
In another case a luxuriantly growing protonema of the same 
Species as above mentioned was placed upon a piece of flower- 
pot and one half covered with earth, the other allowed to remain 
free. Only in one or two cases was a growth of rhizoids noted 
from the part covered with earth. The same result was obtained 
with protonemata of Brywm capillare and Barbula muralis in which 
one half was covered with a screen of black paper. The proto- 
nemata lost their chlorophyll content, but did not develop any 
distinct rhizoids. From these results it is seen that although 
exposed to darkness and also grown on earth, a rhizoid produc- 
tion only rarely occurred. A culture of protonema of Barbula 
muralis which was grown in the light produced distinct rhizoids 
after about eleven weeks of growth. Here then is a case of the 
production of rhizoids in direct illumination. Bryum capillare 
and arbula muralis \eaves were grown under water and a lux- 
uriant protonema growth obtained. It might be thought that 
growing under these conditions, the protonemata would retain 
their more algal nature and not produce new leafy shoots, but 
in the case of Bryum, buds made their appearance after the 
usual length of culture. There was, however, a difference in the 
form of growth. In Bryum and Barbula the lateral branches 
grew quite slender and tapering, while in the cultures on flower- 
pot they were more robust and of equal diameter throughout. — 
In Barbula these side branches frequently possessed oblique 
cross-walls, while Bryum generally had perpendicular cross- 
walls. This manner of growth has been mentioned by Goebel™ 
for a protonema of Physcomitrium pyriforme when grown in 
water. He compares these side branches to rhizoids and makes 
the statement that they evidently correspond to rhizoids. It 
might be inferred that the lack of rhizoid production in these 
* Flora 72:8. 1889. 
