Hoyt: CULTURES OF SPIROGYRA 335 
required concentration with either ordinary or nontoxic distilled 
water. The reactions to litmus paper of the solutions thus pre- 
pared were as follows: Sachs’s, very slightly acid; Knop’s, acid; 
Molisch’s, slightly acid; Crone’s, neutral. The salts used were, 
in every case, those of Merck. 
The results obtained from the various cultures in these nutrient 
solutions are given in TABLE I, where each culture is denoted by a 
letter indicating the condition of the culture during the period of 
the experiment, the number of letters thus denoting, in each case, 
the number of times that the experiment in question was per- 
formed. The durations of the cultures are also given. The same 
notation is used in TABLES II, II, and v. 
Using nontoxic distilled water, prepared in a manner to be 
described later, the best growth was shown with all the media in 
concentrations containing from 0.05 to 0.1 per cent of total salts. 
In these concentrations of the solutions of both Molisch and Crone, 
Spirogyra was kept growing vigorously, in apparently perfect 
condition, for a period of about two months, at the end of which 
time the experimentation was discontinued. Crone’s solution 
seemed slightly more favorable to the organism than did that of 
Molisch; Sachs’ solution produced a fair growth; while Knop’s 
medium was distinctly unfavorable, probably because of the 
marked acidity, free acid being injurious to many algae (10). 
No doubt still other media might prove as favorable as those of 
Molisch and Crone. 
When ordinary distilled water was used in preparing the solu- 
tions a good growth was never obtained, but the results in both 
Molisch’s and Crone’s solutions seemed slightly better in con- 
centrations of from 0.5 to 1 per cent than in weaker solutions. 
This will be discussed later. 
The addition of one per cent of agar to the nutrient solutions, 
the Spirogyra filaments being laid on the surface of the coagulated — 
pinecone ay 
Sacus Knope MOLiscH CRONE 
I g. KNOs, 1 g. Ca(NOs)2, 1 g. (NH«)2HPOs, 1 g. KNOs, 
0.5 g. NaCl, 0.25 g. KNOs, 0.5 g- KH2POs, 0.5 g. MgSO«, 
0.5 g. CaSOx, 0.25 g. MgSOz, 0.5 g- MgSO, 0.5 g- CaSOx, 
9.5 g. MgSOu, 0.25 g. KH2POx, 0.5 g. CaSOu, 0.25 g- Cas(POs)2, 
0.5 g-CaHPO,s, 0.125 g. KCL, Trace FeSO.. 0.25 g. Fes(POs)s. 
Trace FeClo. Trace FeCl: 
