MICHIGAN ACADEMY OF SCIENCE. 306 



RESISTANCE TO DESICCATION. 



The spores of M. sarcinaeforme can withstand a long period of desicca- 

 tion. As previously remarked, the material from which the fungus was 

 first isolated was 18 to 20 months old. Furthermore, it had been kept in 

 a drawer where the temperature for hours at a time reached 65° C, 

 (drawer was over a steam radiator). In November, 1915, the fungus was 

 again isolated from material collected in the fall of 1911. Desiccated 

 spores kept on a cover glass for 9 months were found to be viable. 



The multicellular structure of the spore and its large size give it more 

 opportunity to withstand desiccation. There is always a possibility of 

 at least one of the many cells of the spore to survive the desiccation 

 process, thus providing for the further propagation of the fungus. 



In the case of bacteria, Staphylococci (in clusters) are known to be 

 far more resistant to desiccation than Diplococci or Streptococci. Again 

 the presence of Sarcinae in dust would indicate that its packet-like struc- 

 ture (to which the spore form of M. sarcinaeforme is analogous) is an 

 important factor in its resistance to desiccation. 



LIGHT RELATIONS. 



To determine the light relations of this fungus, four different kinds 

 of media were inoculated in duplicate, wrapped in black paper, and put 

 away in a dark cupboard. A similarly inoculated set of cultures were 

 kept in the light. Two weeks later the tubes were examined and the 

 amount of growth in both was found to be about the same. This fungus 

 does not, therefore, show marked reaction to light. 



Effect of Direct Sunlight: 



The usual method of determining the toxic effect of sunlight upon a 

 fungus is to place a petri dish containing the freshly poured culture, in 

 direct sunlight for various lengths of time. 



Discs of filter paper, 1 cm. in diameter were cut with a cork borer, 

 a pin run through each, near the edge, and then dry sterilized. A drop 

 of spore suspension was then placed upon the upper side of each disc 

 and the water permitted to evaporate rapidly in vacuo in a desiccator 

 containing CaCl2. The discs were then mounted in a horizontal position 

 by sticking the pins into a cardboard box, and then placed in the direct 

 sunlight. At intervals of 10 minutes three of these discs were removed 

 and each dropped into a tube of clover juice medium. The discs were 

 shifted at times, so as to be constantly in the direct rays of the sun. 

 This experiment was run June 28th, 1915, between 9:30 and 11:40 A. M. 

 The temperature in the direct rays of the sun varied from 29 to 34 °C. 

 Within the usual time growth appeared in all the tubes showing that 



