1898 } REGENERATION AS EXHIBITED BY MOSSES 177 
number of rhizoids from the surface uppermost. This would 
tend to corroborate the statement already advanced that 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 illu- 
minated 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 illuminated 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?3 has shown that the moss-plant is 
distinctly negatively geotropic, but that with illumination from 
below, the shoots grow towards the light, the influence of gravity 
being overcome by that of light. This I have been able to sub- 
stantiate 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 trans- 
versely 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 whether it was possible for the cells 
from the costal region to give rise to buds, the lateral halves 
*3 Rey. gén, de Botanique 3 : 406-411. 1891. 
