18 BOTANICAL GAZETTE [JANUARY 
sprout of each plant was measured, the recorded length being takea 
from the surface of the pot to the tip of the leaf. The average of 
these leagths for a given pot constitutes the average length of sprout 
recorded for that culture. The plants were then cut off close to the 
surface, cut into short pieces into a crucible, and the green weight 
recorded. After drying in a Bausch and Lomb oven for 5 to 7 days 
at 100-110° C. the dry weight was recorded. 
Corks fitting the bottles used for solution cultures were perforated 
with a small cork-borer so that six plants could be grown in each of 
the larger bottles. The corks were thea boiled for several hours, 
with numerous changes of water, in order to remove any possible 
injurious ingredients. After being dried, they were boiled in paraffin, 
to insure an upper surface that could not be wetted. The wheat 
plants were now inserted through the perforations, so that the seed 
and roots were below the lower surface of the cork and in the solution. 
The holes were loosely plugged with ordinary cotton to fastea the 
plaats and to prevent evaporation. Bottles were weighed from 
time to time and solution replaced from a pipette, record being kept 
of the amouat lost by traaspiration from each bottle. The length 
of the sprout was measured from the upper surface of the cork to 
the tip of the longest leaf of each plant as in the case of the soil cul- 
tures. The green and dry weight of the whole plant from the solu- 
tion cultures was always taken; while ia the soil cultures only the 
aerial portion is available for comparison. 
Fungus contamination in solution cultures was practically over- 
come by sterilizing seeds in a 2 per cent. CuSO, solution for three- 
fourths of an hour; washiag afterwards in sterilized water; planting 
in sterilized sphagnum, and transplanting in a sterile chamber into 
sterilized solutions. The sterile chamber was a box 100 50X50°™, 
with a glass cover and a glass windowin front. Rubber-cloth sleeves 
which fit snugly around the wrists of the operator were provided. 
The chamber was thoroughly sprayed with CuSO, before using. 
The series in solution and in soil were grown at the same time, 
under the same conditions of light, heat, and other external factors. 
Experimentation 
Responses to toxic salts are of two kinds: (a) acceleration and 
(>) retardation of growth which progresses as the concentration in- 
