Botany. — “Concerning the Influence of Light and Gravitation on _ 
Pellia epiphylla”” By Dr. Ta. Weevers. (Communicated by 
Prof. F. A. E C4 Want) 
(Communicated at the meeting of April 30, 1921.) 
Recent investigations concerning the influence of light and gravi- 
tation on the growth and the curvature of plants have been under- 
taken only with some particular objects. Although this yields 
the advantage that such investigations may be complemental to 
each other, it yet seemed to me that the study of quite another 
object might open up new points of view, or might give rise to 
new questions. 
I considered Pellia epiphylla Corda to be a suitable object, as it 
offered various advantages, notably for the study of the growth of 
sporogonia under the influence of stimuli of light and gravitation. 
To my knowledge nothing kas been published on this point ever 
since 1874, when Askrnasy') dealt with it in a few paragraphs. 
After the eell-division has taken place, the sporogonia of Pellia 
come to a period of rest in winter. At its close the rising tempera- 
ture brings about a growth of the stem-cells, slow at the beginning, 
afterwards more rapid; this process does not require illumination, 
an increased content of water of the soil accelerates it. The sporo- 
gonium-stem begins to grow within 3—5 days, only the base remains 
enclosed by the calyptra. The length of the stem increases from 2 
or 3 mm. to 6 or 8 em. The number of cells remains unchanged, 
so does the diameter approximately, but their length is increased 
from 25—30 u to 800—900 u, their volume becomes about 30 times 
as large again. The inner cells are torn up and the stem becomes 
hollow, finally dextro-torsion ensues. The starch, which fills up the 
cells completely during the winter-rest, is entirely lost during the 
growth of the cells; the chlorophyl-granules also disappear more 
and more, so that the green colour of the tissue in the fullgrown 
parts becomes transparent; only the oily bodies”) or elaioplasts *) 
in the outer cells remain unchanged. 
The osmotic pressure, which prior to the longitudinal growth is 
1) ASKENASY 1874. Botan. Ztg. 32. 
*) W. PFEFFER 1874, Die Oelkörper der Lebermoose Flora. 
5) J. H. WAKKER, Pringsh. Jahrb. Bd. 19. 
