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exactly the same conditions did. This is presumably explained 

 by the small weak stem, which when robbed of its leaves is 

 not able in itself to afford material for the growth of new 

 shoots, in additions to what is used to produce the abundant 

 growth of rhizoids and protonema. 



BARBULA MURALIS. 



The leaves of Barbula produce protonema with great 

 readiness. Cultures of the detached leaves were made for 

 both light and dark, and the best results were obtained from 

 those upon pieces of flower-pot. After a lapse of about a 

 week an abundant growth had appeared in the cultures in 

 the dark as well as in the light. The first growth was 

 colorless, with slightly oblique cross-walls, and no Chlorophyll 

 except what was derived from the leaf cell. Those which 

 remained in the light for the entire period soon showed a 

 very vjgorous growth, with luxuriant branching and the absence 

 of any bud formation. The walls of the main axes after 

 a time turned brown and had more of a rhizoid nature. The 

 side branches, although at times slender and tapering and 

 now with oblique cross-walls, now with perpendicular walls, 

 were decidedly protonema in character and possessed an 

 abundant Chlorophyll content. A thick net of interlacing 

 protonema filaments was obtained from the culture in the 

 light. At the end of ten weeks the network was several 

 centimeters in extent, and not withstanding the fact that 

 it had been exposed to the light in the laboratory window, 

 no bud formation had resulted. The suppression of bud 

 formation could not have been due to the lack of sufficient 

 light, since as exposed in the window the illumination was 

 quite intense. Up to this time the culture had produced no 

 growths which I could call rhizoids. The cultures which 

 remained in the dark produced only long , very sparcely 

 branched filaments which in their further growth tended 

 more to a rhizoid nature, with no Chlorophyll, brown walls 

 and always oblique cross-walls. 



