— 28 — 



same conditions as the detached leaves gave rise to no 

 protonema from the leaves. That the production of protonema 

 was not called forth by cutting was shown by the experiments 

 in which half of the leaf tip was cut away while the outer 

 half was left in connection with the stem. Under these 

 condition the portion of the leaf remaining in connection 

 with the stem showed no growth. A complete Separation 

 of the leaf from the stem is then necessavy to call forth 

 the power of the leaves to produce protonema and buds. 



The defoliated stems of Atrichum when placed under 

 conditions favorable to growth give rise to new shoots as 

 axillary branches. This regeneration by means of new side 

 branches occurred as readily in darkness as in light. In the 

 dark the shoots grew more rapidly, producing more slender 

 stems with reduced leaves. The tendency to apical production 

 of shoots was not well marked, the shoots appearing at 

 various points along the stem from base to apex. No new 

 production of rhizoids or protonema were obtained from the 

 stems under any conditions, although the cultures were kept 

 for several months. Whole plants under exactly the same 

 conditions as the defoliated stems produced new shoots as 

 axillary branches but not in as great abundance as the de- 

 foliated stems, showing that the production is accelerated 

 by defoliation. 



POLYTEICHUM COMMUNE. 



Cultures of leaves were made the same as for Atrichum, 

 but it was not tili the end of about six weeks that the 

 growth of protonema was observed. The protonema were 

 similar in nature to those already described for Atrichum, 

 colorless walls and oblique cross-walls in both light and 

 dark. A peculiar aggregation of branches occurred quite 

 frequently an example of which is shown in Fig. 36, thus 

 forming an assimilating organ, while the production of buds 

 came later. In the protonema grown in the dark the cells 

 were longer, without Chlorophyll and the branching was 

 more or less suppressed. 



