290 Marine Microbiology 



the fungus, the subsistence level at tiiis temperature was presumed 

 to be practically the same as the subsistence level at other 

 temperatures. The "subsistence medium" was defined as that 

 combination of glucose and yeast extract which at minimal con- 

 centi'ations would support apparently normal morphology and 

 sporulation. Z. eistJa has some growth on a medium which has 

 some yeast extract, but never grew on a medium containing 

 glucose only. When no glucose was present with the yeast ex- 

 tract, colony diameter increased rapidly, but the mycelium was 

 sparse. When the lowest concentration of glucose (0.0125%) was 

 added with the lowest level of yeast extract (0.0125%), colony 

 diameter increased at the same rate as when tlie greatest amounts 

 of glucose (0.25%) and yeast extract (0.05%) were added, but 

 sporulation was weak. Spore formation, varying with the amount 

 of glucose supplied, was satisfactory on 0.036 per cent glucose. 

 Although vegetative growth measurably lessened if the level 

 of yeast extract was reduced to 0.007 per cent, it did not com- 

 pletely stop. The final medium for testing the effect of subsistence 

 nutrient conditions on the Phoma pattern consisted of artificial 

 sea water as in the first experiment, 0.007 per cent yeast extract, 

 0.036 per cent glucose, and 0.85 per cent lonagar. A full series 

 of cultures was incubated over the entire temperature range. 



The criterion in all experiments was increase in colony diam- 

 eter, measured to the nearest millimeter across the least dimen- 

 sion. After the first five or six days, readings were made every 

 two days as long as the growth rate remained steady or until 

 the mycelium of the fastest growing culture reached the edge 

 of the dish. "No growth," for the purposes of these experiments, 

 was defined as no visible mycelial production after three weeks 

 of incubation. All experiments were made in triplicate. 



RESULTS 



Z. eistla showed a typical Phoma pattern, witli the best low- 

 temperature growth at low sea water salinity, and the best high- 

 temperature growth at high salinity. At 6 C, 16 C, and 20 C, the 

 peak growth range varied from S%o to 25 S%o, At 25 C the 

 peak was at about 28 S%o; at 30 C, about 58 S%o; and at 37 C 

 it was between 55 and 80 S%o ( Fig. 1 ) . Although colony diameters 



