— 40 — 



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 protonema of Bryum 

 capillare and Barbula muralis in which one half was covered 

 with a screen of black paper. The protonema lost their 

 Chlorophyll content, bud did not develop any distinct rhizoids. 

 From these results it is seen that although exposed to darkness 

 and also grown on earth, a rhizoid production 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 

 Barbula muralis leaves were grown under water and a 

 luxuriant protonema growth obtained. It might be thought 

 that growing under these conditions. the protonema 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 pots 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 1 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 



1 Flora 72 : 8. 1889. 



