— 17 — 



of the leaves from the stem is necessary in order to call 

 forth the formation of protonema. 



The experiments with the leaves which had portions of 

 the stem torn away with them showed the stem cells to have 

 a remarkable power of protonema production. A series of 

 cultures was made in which the leaves were eutirely stripped 

 from the stems and the stems cultivated in both light and 

 dark. The stems produced new shoots as lateral branches 

 with remarkable rapidity. After a lapse of only three days 

 the new shoots had reached a length of nearly two milli- 

 meters. No distinct tendency to the appearance of the new 

 shoots from the region of the morphological apex of the old 

 shoot could be detected. Generally , however , a shoot was 

 formed just back of the apex, but in the majority of cases 

 they were produced at other points along the stem, and even 

 from the very base. Occurring at the same time with the 

 production of new shoots was an abundant growth of proto- 

 nema from the stem for its entire length. The regeneration 

 by new shoots was always in the way of axillary branches, 

 in a manner similar to that which often occurs in nature. 

 The protonema were not however confined to the leaf axils 

 but grew as well from cells removed from the axillary regions. 

 In the cultures in the light, tbe protonema originated gener- 

 ally from the side of the stem which was uppermost, while 

 rhizoids were produced from the contact side and in greater 

 abundance from the region of the stem which had formed a 

 new shoot. This is shown in Fig. 12. The cultures in the 

 dark showed very rarely a protonema production , and in 

 neither light nor dark was any bud formation noted from the 

 stem. protonema. In several cases where the receptacles with 

 the perichaetial leaves were placed in culture, an abundant 

 protonema production was noted from the end cells of the 

 receptacle. A dissection showed these protonema to originate 

 from the cells lying between the bases of the anthe- 

 ridia archegonia, and paraphyses, and also from the basal 

 cells of the paraphyses as shown in Figs. 10, 11. All attempts 

 to obtain protonema from the paraphyses when separated from 



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