464 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
except with calcium nitrate replaced by potassium nitrate in a second series. 
A third series with zinc sulphate added to Richards' solution was arranged. 
These series were prepared in triplicate and with the same precautions 
as used in the preceding experiment. The organisms used were selected to 
represent as wide a range of parasites as could be obtained from the stock 
cultures of the laboratory. The experiment was continued for each or- 
ganism until growth seemed to stop. The organisms used and the results 
are tabulated in table 2. 
Table 2 
Richards' Solution, 
Richards' Solution 
Calcium Nitrate 
Richards' 
Plus 5 Mg. 
Substituted for 
Solution 
Zinc 
Organism 
Potassium Nitrate 
Sulphate 
Dry Wt.* 
pH 
Dry Wt.* 
pH 
Dry wt.* 
pH 
.2199 
4,2 
.2404 
5-8 
.2191 
6.3 
Phoma apiicola 
.2798 
5-2 
.1427 
6.0 
.1963 
6.0 
Fusarium conglutinans 
.1628 
6.0 
.1669 
6.4 
.1560 
6.6 
.3750 
5-2 
.3003 
5-4 
•3509 
5-4 
.3451 
6.4 
•341 1 
6.8 
.3118 
6.8 
Fusarium hatatatis 
.2391 
6.1 
■2377 
6.3 
.2501 
8.0 
F. radicicola 
.2666 
8.0 
.3224 
6.8 
.2561 
7.0 
Sclerotinia libertiana (strain i) 
•4545 
3-8 
•4675 
4.2 
•4391 
3-8 
.2132 
S. libertiana (strain 2) 
.1963 
3-0 
.2153 
3-0 
.2052 
3-0 
Rhizoctonia solani 
.1055 
No growth 
No growth 
Macrosporium sarci?iaeforme 
.2777 
6.8 
.2801 
6.6 
.2683 
6.6 
Sphaeropsis malomm 
•3139 
3.6 
■3751 
6.8 
.3689 
6.8 
Sterigmatocvstis violae 
.3264 
6.0 
.2884 
6.0 
•2435 
6.0 
.3272 
•3563 
•3363 
Ascochyta pisi 
.2677 
6.2 
.3782 
6.4 
.3278 
8.0 
Colletoiricum lagenaria 
lost 
Dothidella quercus 
.3652 
6.6 
.2411 
6.5 
•2999 
6.5 
* Average for three cultures. 
Summarizing the results of table 2, calcium is found to be generally 
beneficial. In the case of four organisms it retarded growth. In the 
remaining cultures it was stimulative or exerted no action. Rhizoctonia 
solani grew only when calcium was present. The importance of the role of 
calcium, however, cannot be estimated from the results of this experiment, 
as we have no proof that we have been using it in its proper proportions. 
Zinc sulphate gave slightly beneficial effects with only two organisms, 
Dothidella quercus and Phoma apiicola. 
A striking example of color formation was shown in the case of Fusarium 
radicicola which was pink in the solution containing calcium and colorless 
in potassium solutions. The color was destroyed when hydrochloric acid 
was added and could not be obtained again by the addition of sodium 
hydroxide. 
The results of the above described experiment indicate that calcium 
might be classed as one of the essential inorganic elements in synthetic 
solutions for some fungi. Moreover, it would seem that the salt require- 
