— 26 — 



In the material which was accessible to me, most of 

 the stems were bearing young sporogones and had produced 

 in their normal growth an abundance of rhizoids. The defoliated 

 stems when placed in culture did not give rise to any new 

 shoots and no appreciable production of rhizoids was to 

 be noted. 



ATRICHÜM UNDULÄTÜM. 



So far as my knowledge goes, no moss-leaves with a 

 structure similar to that of Atrichum leaves have been known 

 to give rise to protonema. Hence the successful growth of 

 protonema from these leaves is of the more interest. Four 

 cultures of leaves were made : a series of leaves with the 

 dorsal surface uppermost, and another series with the ven- 

 tral surface uppermost, both to be placed in the light; two 

 similar series were placed in the dark Chamber. At the 

 end of a month the first signs of protonema were observed 

 and in the course of a week they had grown to a consi- 

 derable lenght. An examination of all the cultures showed 

 that the protonema in every case originated from the ventral 

 surface of the leaf without regard to the position which it 

 had occupied in the culture. And further, the examination 

 of the whole leaves showed that the protonema originated 

 from the cells lying at either side of the lamellae. The 

 protonema production from this region was quite general 

 throughout the entire length of the leaf. 



In order to determine more closely the origin of the 

 protonema cross sections of the leaf were made. The sections 

 showed that the protonema originated from the large cells 

 of the costal region lying at the base of the outer lamellae. 

 (Fig. 32). The first growth from the leaf, although the 

 cross-walls were predominately oblique, were decidediy proto- 

 nema in character and remained so whether the specimens 

 were grown in the light or dark. The branching was often 

 aggregated in a manner altogether unique, as is shown in 

 Fig. 30 which may be taken as a typical example. In other 

 cases it was more as in ordinary protonema, but the only 



