— 10 — 



exposed to light, they gave rise to an abundance of protonema 

 like branches and numerous buds. 



A culture of leaves with long, sparcely branched rhizoids 

 which had been grown in the dark was removed to the light 

 and allowed to undergo further development. When examined 

 a week later the rhizoids had produced in the apical region 

 an abundance of branches part of which were still rhizoid 

 in character. A large number of the branches were howerer 

 distinctly protonema in nature, the cell-walls colorless, the 

 cross walls perpendicular, the cells short and filled with an 

 abundance of oval Chlorophyll bodies. The rhizoids also 

 contained Chlorophyll bodies but there were fewer in number 

 and of an elongated lenticular form. An enormous number 

 of buds was also formed and in either of two ways: either 

 as a direct modification of a side branch from a rhizoid 

 cell, or as a side branch from one of the lateral protonema 

 branches. This is plainly illustrated in Fig. 6 and 7. 

 Occasionally a bud was formed later near the leaf, but the 

 great majority made their appearance towards the distal 

 exteremity of the rhizoids. 



A question which now presented itself was: Is the 

 continued exposure to light necessary to call forth the 

 production of buds ? In order to determine whether buds 

 would be produced by light induction, leaves were grown in 

 bright light for nearly two weeks and then carefully 

 examiued to see that no buds had been formed. They were 

 then placed in the dark Chamber and after five days the 

 formation of buds was observed. The number was much 

 less than from those leaves in the light, and on account of 

 a lack of food material only a limited growth occurred. Whether 

 this light induction is due to physical or chemical changes 

 in substances already present in the leaf, or to the accumulated 

 products of photosyntax, can not be stated with certainty, 

 but the experiment which follows would indicate that the 

 products of photosyntax are not necessary to call forth the 

 production of a leafy shoot. 



In order to determine whether the products of photo- 



