6o 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
different maintained temperatures were employed, and light was excluded 
from the experiment chambers. The nutrient solutions used were the 126 
3-salt solutions described by the committee on salt requirements,^ and 
each solution was tested for every one of the seven different temperatures. 
These 3-salt solutions are of 6 types,^ according to the salts employed, and 
21 different solutions were tested for each type, each of these having its own 
peculiar set of salt proportions. The familiar triangular diagram was used 
to represent the difference in salt proportions. The salts employed were 
the nine possible combinations of the following six chemical units; K, Ca, 
Mg, NO3, H2PO4, and SO4. No iron was added to any of these solutions. As 
to total concentration, the solutions were all about alike and very weak, 
being only one tenth as concentrated as the corresponding i -atmosphere 
solutions described in the plan above referred to. 
The present paper will be confined to certain points brought out for the 
two temperatures 28° C. and 17° C. (one about optimum and the other dis- 
tinctly below the optimum temperature for the early growth phases of 
wheat). Only those solutions of each of the six types tested will be con- 
sidered that gave the best growth values, determined by the criteria of 
total shoot elongation per culture and average elongation per seedling of the 
cultures, for a period of no hours, beginning with the placing of the seeds 
on the net. The best values obtained for the set of 21 solutions for each 
of the six types for each of the different temperatures tested were considered 
the "good" solutions, if their growth values obtained lay within the upper 
one fourth of the total range of values for the same temperature and the 
same solution type. For example, if the 21 solutions of the type con- 
taining the salts KH2PO4, Ca(N03)2, and MgS04, gave a growth value 
ranging from i.oo to i .80 for the average of both the criteria used, tested at a 
temperature of 28° C, then those solutions whose value lay between 1.60 
and 1.80 would be classed as the "good" solutions for the type at that 
given temperature. The total-shoot-elongation value simply represented 
the total growth obtained from a solution. The average elongation value 
per seedling per culture was obtained by dividing the total shoot elongation 
in centimeters by the number of seedlings the culture contained. The 
reason these two criteria were employed was to offset any appreciable error 
that may accrue in the growth value from a failure of some of the seeds to 
germinate. The following table shows what solutions belong to the "good" 
class for each type and for each of the two temperatures here dealt with. 
In the solution designations, which refer to the triangular diagrams, the 
3 Committee on salt requirements of representative agricultural plants, Division of 
Biology and Agriculture, National Research Council. A plan for cooperative research 
on the salt requirements of representative agricultural plants. Edited by Burton E. 
Livingston. 2d ed. Baltimore, 19 19. 
4 For an outline of the chemical scheme of these six types, on which the committee's 
plan was based, see: Livingston, B. E., and Tottingham, W. E. A new three-salt nutrient- 
solution for plant cultures. Amer. Jour. B3t. 5: 337-346. 1918. 
