1165 
nn IT TS I PS LE EE 
Distance between radium and heart Uranyl-nitrate added to the primary 
(mm.) mixture (mgrms.) 
4 | 5 
3,5 | 6,5 
3 9 
vd) ii A 
2 15 
1,5 18 
I 22 
Chala Ce he SS lee Sh wee BET 
Mesothorium-equilibria — — — — Radium-equilibria. 
O-a method may be found to determine the biological value of a 
radio-active preparation (in a recovering sense). But it is out of 
place here to deal with this practical application. 
Botany. — “The influence of light- and gravitational stimuli on the 
seedlings of Avena sativa, when free oxygen is wholly or 
partially removed”. By Dr. U. P. v. AmwIJDEN. (Communicated by 
Prof. F. A. F.C. Went). 
(Communicated at the meeting of February 24, 1917). 
§ 1. Introduction. 
Our conception of the influence of oxygen removal on geotropism 
and phototropism is mainly due to Correns‘). His method of working 
!) C. Correns. Ueber die Abhängigkeit der Reizerscheinungen höherer Pflanzen 
von der Gegenwart freien Sauerstoffes. Flora 75. 1892. 
