608 ON PLANT GROWTH HORMONES 
auxin solution was, on December 17th, at 4 A.M., six times as active as in 
the forenoon of the preceding day. A potency which we had previously 
Standard variations 
‘ Sent.30% Oct.1" 1932. 
o 70° per G 
Nov. 4% Nor:S*1932. 
regarded as characteristic of an individual day, in reality therefore applies 
to the actual hour of the experiment. 
After consultation with Prof. Ornstein of the Physical Institute and his 
6 & 0 2 W 16 8 20 2 2% 2 
ae wall perg Jan.20% Fan21°1933. 
FO —e- 
e o- Tae, 
60° ZUR 
Toten 
assistant, Mr. Jan Went, we carried out further series of experiments in 
order to elucidate the changes in the potency of our standard. We tested 
the potency of auxin solutions on seedlings grown in a Faraday cage, in 
