74 THE LILAC MILDEW. 



special shell, enclosing a number of pores in sacs in which 

 the spores are formed. 



There is not much known of the manner in which 

 these fruits pass the winter and give rise in the spring to 

 another growth of mildew. It is plain from the structure, 

 however, that the spores escape from the sacs through the 

 thin spot at their apex, but not so evident how they 

 escape from the shell of the fruit and reach the host plant, 

 though their escape is probably secured through the 

 gradual decay of the shell. The appendages we may 

 suppose are of some service in distributing the fruits. 



