The Effects of Osmotic and Nutritional Variation 287 



Several modes of action appear possible. Inasmuch as many 

 of the components of sea water are usable in metabolism, the 

 heightened salinity optimum at higher temperatures might be 

 a nutritional requirement, and if it is, tlie salt or salts concerned 

 might be replaced by others. If the phenomenon is due to the 

 action of some specific enzyme or enymes, the metals especially 

 would be critical components of the medium. The effect might 

 also be due to membrane activity, in which case specific salts 

 might again be critical. Still another possibility is that the phe- 

 nomenon is primarily an osmotic one, in which the salt could be 

 essentially a diluent of water. If that is so, one should, by using 

 any non-toxic solute, be able to produce growth curves similar 

 to those obtained from saline cultures. 



The experiments described in the present paper were per- 

 fonned in an effort to clarify the problem of why incubation 

 temperature and salinity are interrelated, and to find what other 

 factors, if any, are involved in the laboratory culture of marine 

 fungi. 



MATERIALS AND METHODS 



The present investigations were conducted with a culture 

 of Zalerion eistla Moore and Meyers, from Argentia, Newfound- 

 land, supplied by Dr. S. P. Meyers of the University of Miami 

 Marine Laboratory. The fungus was routinely cultured on a 

 medium containing 0.3 g NaNO., 0.05 g KCl, 0.05 g MgS04-7H20, 

 0.001 g fen'ous acetate, 0.1 g Difco yeast extract, 0.5 g glucose, 

 and 1.5 g agar per 100 ml, a mixture which will be referred to 

 as the basic medium. 



In the first experiment, which demonstrated the response 

 of Z. eistla to temperature and salinity, we used artificial sea 

 water made up according to Provasoli et al. (6), with total salt 

 content, by weight, of 1.0 per cent, 2.5 per cent, 3.4 per cent, 

 5.5 per cent, 8.0 per cent, and 10.2 per cent. The medium in each 

 run contained 0.1 per cent yeast extract, 0.5 per cent glucose, 

 and 1.5 per cent agar. Petri dish cultures were incubated at 6 C, 

 15 C, 20 C, 25 C, 30 C, and 37 C. The 6 and 37 incubators varied 

 about 1 C, the others less. Although the plates in the 30 and 

 37 incubators were kept in covered containers lined with moist 

 paper, some drying of the media occurred. Salt concentrations at 



