M. A. Bailey 105 



of temperature and greater degrees of desiccation than those which 

 fall on to leaves growing lower down. 



It is possible that these or some similar factors may have a favourable 

 influence on the germination of the spores, thus producing the effect 

 described. 



The favourable effect of cooling on the germination of spores of 

 Cystopus candidus has been shown very clearly by Melhus 1 , and 

 Eriksson and Henning 2 , working on the Uredineae, found that accidio- 

 spores which had been placed on ice for a time gave a much higher 

 percentage of germination than those which had been left throughout 

 at the temperature of the room. 



1 Wisconsin AgL Expt. Station 28$ Ann. Rept, 191 i. 



2 Die Getreideroste, p. 73. 



