[Vor. 1 
174 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
Nitrogen-free Water.—The distilling apparatus used was, in 
general, like that described by Jones and Mackay (16) for the 
preparation of water with a very low electrical conductivity, 
except that the water was triply distilled in place of doubly, and 
from glass throughout in place of being condensed in a block tin 
tube. Fig. 1 represents the distilling apparatus, and it need 
only be pointed out that flask іп was added to obviate any 
possibility of contaminating the distillate with spray from 
flask п. The water obtained from this still gave uniformly 
negative results when tested for ammonia, nitrites and nitrates. 
Fig. 1. Distilling apparatus for nitrogen-free water 
Cultural Apparatus.—One hundred се. flasks, carefully cleaned 
in acid-dichromate cleaning mixture, rinsed in nitrogen-free 
water and dried, were connected in series of ten each in the 
1912 experiment (eight in the 1913 experiment) by means of 
glass tubing and rubber stoppers as shown in pl. 3 fig. 1. The 
glass tubing was cleaned in the same manner as the flasks, and 
the rubber stoppers were boiled in dilute alkali, then in dilute 
hydrochloric acid, and subsequently washed with distilled and 
nitrogen-free water. Into each flask of the 1912 experiment an 
accurately weighed 40-gram quantity (in the 1913 experiment 
