— 34 - 



leaves in each case being dorsal side and part benig ventral 

 side up. At the and of five days both protonema and buds 

 had been produced in the light , and a careful examination 

 showed that the majority of the growths originated froin 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 protonema branches, but remained distinctly rhizoid 

 in natnre even in the light. The brauching of the protonema 

 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 

 live days. 



When the lateral naives of the leaves were separated 

 from the costa, they also gave rise to numerous protonema 

 showin g that in the whole leaf the ability of regeneration 

 was present, but that the supply of food material was con- 

 tributed to the cells of the costal region, which produced 

 protonema with greater ease. It has abready 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. The dorsad side of the 

 costa was made up entirely of thick walled cells, hence no 

 protonema production from from the dorsal side occurred. 

 (Fig. 51.) 



Whole plants and plants with the tips of the leaves 

 cut away produced no protonema from the leaves, nothing 

 but a complete Separation of the leaves from the stems being 



