1170 
Botany. — “The influence of temperature on phototropism in seed- 
lings of Avena sativa.” By Miss M. S. pe Vries. (Communi- 
iy ) 
cated by Prof. F. A. F. C. Wenz). 
(Communicated in the meeting of Jan. 25, 1913). 
In connection with Rererrs’ *) investigation on the influence of 
temperature on the geotropic presentation-time in Avena sativa seed- 
lings, I have undertaken experiments to find out how far temperature 
influences phototropism. 
I had originally no intention of making a preliminary statement 
at this stage because some of the experiments are not yet complete, 
but after the publication of Torsten Nyperen’s*) work on the same 
subject in which results wholly opposed to mine are given, it became 
desirable to make a communication now. 
Torsten NyperaH comes to the conclusion that temperature has 
no influence on the process of phototropical stimulation. According to 
him therefore the influence of temperature on phototropism may be 
represented graphically by a straight line. The results [-have ob- 
tained at various temperatures can however be represented by a defi- 
nite optimum-curve. Before I consider the results, I should like to 
say a few words about the method. 
Seedlings of Avena sativa having a length of about 2.5 em. were 
used. The boxes of seedlings were warmed for at least an hour 
beforehand in the thermostat used by Rurcers at the temperature 
to be investigated; they were then exposed to light in the thermo- 
stat and then taken out of the apparatus. The seedlings always exe- 
cuted their curvature at 20° C. While the seedlings were in the 
thermostat, fresh air was drawn through it, moreover the dark room 
in which all the experiments took place was ventilated as much as 
possible. The warming of the thermostat was done by electric lamps; 
gas was not burnt in the dark room, so that the atmosphere was 
as pure as possible. The source of illumination was incandescent 
gas light, placed outside the room; the light entered through a frosted 
glassplate, when the diaphragm was open. 
1) A. A. L. Rureers: The influence of temperature in geotropism. Proceedings 
Royal Acad Amsterdam. Vol XIII, p. 476, 1910. 
A. A. L. Ruraers. The influence of temperature on the geotropic presentation. 
time. Recueil des Trav. Botan. Néerlandais. Vol. IX, 1912. 
2) Torsten Nypered. Studien über die Eimwirkung der Temperatur auf die tro- 
pistische Reizbarkeit etiolierter Avena-Keimlinge. Berichte der deutschen Botan. 
Gesellschaft. Band 30, 1912. 
