Botany. — “The Influence of Light on the Cell-increase in the 
Roots of Allium Cepa’. By H. W. Brrinsonn. (Communicated 
by Prof F. A. F. C. Went). . 
(Communicated in the meeting of October 25, 1919). 
Mrs. DROOGLEEVER FortuyN—vaN LeypEN') has found that the 
cells of young cats increase periodically in such a way, that during 
the night, the number of karyokineses reaches its maximum, and 
in the later morning hours and the early afternoon a minimum 
number is reached. Karsten?) stated likewise that a periodical 
karyokinesis takes place in the young buds of Zeamais, which 
reaches its maximum also during the night. However in the roots 
of Vicia Faba he did not find any periodicity and so he concludes: 
«Das Wurzelwachstum entbehrt der Periodizitét.” During these 
experiments the plants remained in the dark. Now he tried to 
influence the periodicity by exposing the young plants to the light 
of an electric lamp, in which he succeeded. On the other hand he 
did not trace the influence of light and dark on the cell-increase 
in the roots. As the root growth is evidently not a periodical one, 
the influence of light and dark will be most obvious here. 
I chose Allium Cepa to experiment upon, because the Alliumeells 
are easily fixed and stained; because one finds a great number of 
karyokineses in the roottops and because there are a great many 
roots, so that it is possible to examine parts of one and the same 
individual under different circumstances. 
At 8 a.m. 11 a.m. and 3 p.m. I took a few roottips away 
from a germinating onion, which was exposed to full daylight. 
After that I put the same onion in the dark and left it alone 
until the next day, then I took a few tips off at 6 a.m., at 12 
a.m. and at 6.30 p.m., while the onion remained in the dark. 
During these two days the temperature differed '/,° C. (registered 
with a maximum and a minimum thermometer). 
I always took care to take roottips shorter than 25 mm. and 
of about the same length. The roottips were fixed in sublimate 
1) Mrs. DROOGLEEVER FORTUYN— VAN LEYDEN. Proceedings Konink. Akad. Amst. 
Vol. 19. 1916, p. 38. 
2) KARSTEN. Zeitschr. f. Botanik 1915, p. 1. 
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