78 G. F. PAPENFUSS 



ferred to dishes containing the nutrient solution and placed in a 

 cool room with ample light. Direct sunlight should be avoided 

 and the culture solution should be renewed periodically. In cer- 

 tain instances it is desirable to aerate the cultures. 



The nutrient medium which has yielded the most satisfactory 

 results is Erdschreiber solution. It was originally prepared by 

 F0yn (1934, pp. 6-7), although the formula was first published 

 by Hammerling (1931, p. 635; see also 1934, p. 4). This medium 

 is much the same as the one used previously by Schreiber (1927), 

 but differs in the substitution of soil extract for distilled water 

 (hence "Erdschreiber"); and the one of Schreiber was in turn 

 the medium of Pringsheim (1921) which was modified for use 

 with marine organisms. Erdschreiber solution consists of: sea 

 water, i liter; soil extract, 50 cc; NaNOa, o.i gr.; Na2HP04, 0.02 

 gr. (For the method of preparation of soil extract see Hammer- 

 ling, 1931 and F0yn, 1934.) Kylin (1933) and others added to 

 Schreiber's medium 3-5 drops of a i per cent solution of ferric 

 citrate. 



Although it has been established by Pringsheim (1936a) that 

 the growth-promoting substances are organic compounds, their 

 exact nature has not yet been determined (Pringsheim, 1949, 

 p. 42). Kylin (1942) believed that ascorbic acid may be concerned 

 here, at least in part, and he showed (Kylin, 1946a) that in addi- 

 tion to ascorbic acid, aneurine and heteroauxin also strongly 

 stimulate growth in Ulva. 



Schreiber (1935), Suneson (1942, 1943) and KyHn (1943) 

 found that the addition of algal extract to the solution of Schreib- 

 er enhanced growth; and de Valera (1940) and Kylin (1941) 

 estabhshed that in-shore surface water, especially from the Fucus- 

 Ascophyllum zone, was much richer in growth-promoting sub- 

 stances than off-shore water or water from a depdi of 35-40 

 meters. 



Artificial sea water has been used by a number of investigators 

 in the cuturing of algae, sometimes with a good deal of success. 

 Dostal (1929), for example, found that Caulerpa not only grew 

 in it but the plants became fertile. Formulae for the preparation 

 of artificial sea water and references to the extensive literature on 



