— 12 - 



light retards the production of rhizoids, since here each 

 culture was only subjected to half the rays of the 

 spectrum. 



In all of the cultures the buds only originated from 

 the illuminated side of the leaf and the question naturally 

 suggests itself : Is this due to illumination or to the negative 

 geotropism of the moss shoot? In order to determine this, 

 a series of leaves was ilJuminated from below by a mirror, 

 so that light and gravity would be acting in the same 

 direction. After the usual length of time buds made their 

 appearance and that only from the illuminated surface. 

 Bastit 1 has shown that the moss-plant is distinctly negatively 

 geotropic, but that with illumination from below, the shoots 

 grow towards the light, the influenae of gravity being 

 overcome by that of light. This I have been able to 

 substantiate in the case of plants grown from the leaves. 

 Another series of experiments was carried out with leaves 

 illuminated from both surfaces. In order to effect this, the 

 leaves were placed in a Petri-dish and irrigated by means 

 of narrow Strips of filter paper alternating with rows of 

 the leaves. The dish was placed upon a ring-stand and 

 illuminated from below by a mirror. In this experiment 

 I found that the buds originated from both surfaces, thus 

 showing the dependence upon illumination. In another series 

 of cultures the leaves were placed in a vertical position in 

 the soil and in such a manner that the leaf surfaces were 

 parallel to the incident rays of light. These as well as the 

 previous experiments showed the production of buds from 

 both surfaces. 



In the case of whole leaves the buds appeared only 

 near the periphery and within the leaf margin, the cells 

 of the border never producing any growth. The cutting of 

 the leaves transversely did not alter their power of 

 regeneration, both rhizoids and buds being produced in as 

 great abundance as in the whole leaves. In order to show 



1 Rev. Gener. de Botanique 3:406—411. 1891. 



