12 



MASS. EXPERIMENT STATION BULLETIN 368 



viable after subjection to a temperature of 75° C, and no spores remained viable 

 after subjection to 80°. 



Test tubes containing 5 cubic centimeters each of spore suspension were sub- 

 jected to a temperature of — 20° C. for various periods of time; the suspension 

 was then warmed rapidly, poured onto potato dextrose agar, and incubated. 

 Spores subjected to this temperature for as long as 28 days showed no decrease 

 in viability. 



The same strain of the fungus which was used in the inoculations, to be de- 

 scribed presently, was grown on various culture media under identical physical 

 conditions and incubated at a temperature of 25° C, with results shown in Table 1. 



Table 1. — Growth of the fungus as affected by the medium 



Medium Growth in Description of Growth 



7 days 

 (Inches) 



Potato dextrose agar 1 Cottony and white. 



Potato dextrose agar with 



lactic acid added ^ Cottony and white. 



Nutrient agar 1 Center of colony very fluffy, edge thin and 



recumbent. 



Prune agar 1 Recumbent. 



Oatmeal agar 1 Similar to growth on prune agar. 



Malt agar 7/8 Mycelium coarsely fluffy and quite sparse. 



Corn meal agar 7/8 Colony definitely zoned, very sparse, with 



many spore masses visible to the naked 

 eye. 



The same strain was grown on potato dextrose agar at various temperatures, 

 to determine the effect of temperature on the physical properties of the colony. 

 Results are shown in Table 2. 



Table 2. — Growth of the fungus as affected by temperature 



Temperature Period of Extent of 



°C. Time Growth 



25-30 24 hours 1 cm. 



20 7 days 14 mm. 



10-15 7 (lavs 5 mm. 



Description of Growth 



Cultures of fungus which had been 

 previously isolated from wood as 

 gray cottony colonies were white 

 and recumbent with a v',ry even 

 edge. 



Mycelium slightly more fluffy than in 

 cultures grown at 25'-30^ 



Mycelium white and recumbent. 



The formation of spore heads (Fig. 8) in the Van Tieghem cells, where the 

 spores produced hyphae on potato dextrose agar, occurred within two to three 

 days after the germination of the sjiores. All three types of conidiophorcs de- 

 scribed by Buchanan^ were formed. There were some aerial spore heads, some 

 subsurface spore heads, and innumerable free-floating spores on the surface of 

 the agar. The spore masses, of which he speaks, were not observed in these 

 preparations, but were found in great quantity on the surface of many of the 

 petri dish cultures; some of these masses were as large as 2 millimeters in diameter. 



■•a brief statement of Buchanan's description is given on pane S of this paper. 



