EFFECT OF LOW TEMPERATURE 121 



present. Merulius lacrymans, or 'dry rot,' also often de- 

 velops monstrous forms when growing in dark places, 

 whereas when developed under normal conditions, the 

 entire plant forms a thickish crust attached at every point 

 to the matrix upon which it is growing. Biffen finds that 

 Agaricus velutipes^hen. grown as a pure culture, assumes ab- 

 normal forms in darkness, the pileus being arrested. This is 

 perhaps not remarkable, my own experience being that the 

 sporophores of all fungi, excepting conidial forms, are 

 always more or less abnormal when grown as pure cultures, 

 even under the most favourable conditions. 



Biffen, Journ. Linn. Soc., 34, p. 147 (1898). 

 Brefeld, Unters. iiber Schimmelp., Heft 3, p. 87, and 

 Heft 4, p. 76. 



Ferguson, U.S, Depart. Agric.^ Bull. No. 16 (1902). 

 Klein, Bot. Ztg., 1855. 



EFFECT OF LOW TEMPERATURE ON THE 

 GERMINATION OF SPORES 



Eriksson has shown that the capacity for germination 

 is in some instances accelerated by exposure to cold. In 

 Aeddium berberidis this was observed in seven out of twelve 

 experiments when slightly cooled (not exceeding o C.) ; 

 and in four out of five instances when strongly cooled 

 (below o C.). On the other hand, an extremely low tem- 

 perature was found to retard germination. 



Chodat determined that the spores of Mucor mucedo do 

 not benefit by exposure to very low temperatures ( 70 

 to 110 C.). The fungus, however, when exposed to this 

 low temperature for sixty hours, is not killed; the mycelium 



