Strawberry Mildew. 



199 



however, most rapid and destructive in its action as 

 the fruit approaches ripeness. As in the case of the 

 allied hop-mildew, which runs " with great rapidity 

 in the hop cones as they approach maturity, the full 

 virulence of the strawberry mildew is concentrated upon 

 the ripening- fruit, so that the latter is spoiled before it is 

 fit to pick. It could not be ascertained that there were 

 any special causes for the unusual attacks of this 

 fungus during the past season, nor could they be traced 

 to any particular methods of treatment. Plants on dry and 

 damp soils seemed to suffer alike, and all kinds of straw- 

 berries were equally affected. Atmospheric conditions 

 were not materially abnormal during the growth of the 

 plants, except that there were some sharp alternations of 

 temperature, and a period of drought, during which the 

 development of the fruit was temporarily checked, followed 

 by copious showers, causing quick growth. 



This fungoid attack must not be confounded with that of 

 the fungus termed Sphcerella fragaria, which is confined to 

 the leaves, nor with that of Glceosporiiiui fragaricEy of similar 

 habit. These fungi appear in spots upon the leaves, and 

 by their action upon them indirectly affect the production 

 of fruit. As has been shown above, the SphcErotheca pa?inosa 

 directly infects the fruit and makes it unfit for use. 



SphcBrothcca panuosa is a member of the family of fungi 

 classified as Erisypheoe. The well-known species dreaded 

 hy ho-^-growersySphcerothecayPodosphcEra) casiagnei,\s its close 

 ally. Like the other members of the family of Erisyphece, this 

 fungus is parasitic upon the surfaces of the leaves and fruit 

 of plants. It does not invade the stems, leaves, stalks, and 

 fruit in the same way as the potato fungus, Phytopthora 

 infestans, but its mycelium merely penetrates the cells of the 

 epidermis from which it derives nourishment, thereby weaken- 

 ing and injuriously affecting the infected plants. 



The life history of the fungus is comparatively clear. It 

 commences with the spores of an ovoid shape liberated from 

 the winter cases — pcrithecia — which have passed the wintei 

 upon parts of the plants, upon the ground, or upon other 

 host plants of different species. This fungus is found also 



