SPHAEROTHECA 



147 



dispersed by wind, rain, insects, birds, etc., and each one 

 that alights on a young, growing part of a gooseberry bush 

 is capable of infecting the plant, and starting a new centre 

 of disease. This mode of infection may continue until late 

 in the autumn, under favourable weather conditions, or 



FlG. 37. Sphaerotheca mors-uvae. 1, showing mildew on leaf and fruit ; 

 2, winter stage on a shoot ; 3, perithecium or winter fruit ; 4, ascus con- 

 taining spores ; 5, a chain of conidia or summer fruit ; 6, conidia showing 

 fibrosin bodies in their interior; 7, a branch that has been injured by 

 aphides (green fly) at the tip. The recurved spines and brown colour are 

 characteristic. Figs. 1, 2, and 7, nat. size ; remainder highly mag. 



when an autumnal expansion of buds follows early pruning. 

 As the season advances the white mildew, which at first 

 resembles in general appearance the well-known hop mildew, 

 and rose mildew, becomes denser in substance, more especi- 

 ally on the fruit and shoots, changes to a dingy brown colour, 

 and becomes studded with the dark-brown perithecia or 



