SOIL ALGAE 221 



containing melted and cooled (42°C.) agar that has been well shaken. 

 The colonies are allowed to develop in the solid agar in bright sunlight, 

 and are then cut out as^eptically and transferred to fresh media. The 

 process may have to be repeated. 18 



Cultivation of soil algae. For the cultivation of soil algae, the above 

 three solutions, either in liquid form or with 1.5 per cent agar, can be 

 used. A medium containing 1.475 gram of Ca(N0 3 ) 2 -4H 4 0, in place 

 of 0.5 gram NH 4 N0 3 , per liter has been used 19 with good results. For 

 the cultivation of diatoms, a modification of Miquel's 20 medium, con- 

 sisting of the following two solutions has been found 21 to give satisfac- 

 tory results. 



A. 20.2 grams KN0 3 in 100 cc. of distilled water. 



B. 4 grams Na 2 HP0 4 in 40 cc. water + 2 cc. concentrated HC1 + 2 cc. FeCl 3 

 (melted at 45°C.) + 4 grams CaCl 2 dissolved in 40 cc. water. 



Forty drops of A and 10 to 20 drops of B are added to 1 liter of distilled water. 



In addition to the above media, the following two solutions are very 

 favorable for the growth of algae : 22 



Pringsheim solution Benecke 23 solution 



NH.,MgP0 4 1.0 gram Ca(N0 3 ) 2 0.5 gram 



K 2 S0 4 0.25 gram MgS0 4 -7H 2 0.1 gram 



Fe 2 (P0 4 ) 2 trace K 2 HP0 4 0.2 gram 



Water 1000 cc. FeCl 3 trace 



Water 1000 cc. 



The following solid medium can be used for the cultivation of algae : 



Chodat 2i medium 



Ca(N0 3 ) 2 1.0 gram FeS0 4 trace 



K 2 HP0 4 0.25 gram Distilled water 1000 cc. 



MgS0 4 -7H 2 0.25gram Washed agar 10 grams 



KC1 0.10 gram pH 5.3-5.5 



18 See also Bristol Roach, 1926 (p. 225). 



19 Wann, F. B. The fixation of nitrogen by green plants. Jour. Bot. 8: 1-29. 

 1921. 



20 Miquel, P. De la culture artificielle de3 diatom6es. Ch. I, Le Diatomiste. 

 1: 93-99. 1890. 



21 Ailen, E. J., and Nelson, E. W. On the artificial culture of marine plankton 

 organisms. Jour. Marine Biol. Assoc. 8: No. 5. 1900. 



22 Pringsheim, 1924 (p. 218). 



23 Benecke, W. tJber Kulturbedingungen einiger Algen. Bot. Ztg. 56: 83- 

 97. 1898. 



24 Chodat, R., and Grintzesco, J. Sur les m6thodes de culture pure des algues 

 vertes. Actes Congr. Intern. Bot. Paris. 1910, 157. 



