200 



Strawberry Mildew. 



upon rose trees, peach and apricot trees, and plants of various 

 kinds. From the spore a white mycelium is formed, having 

 many branches, and fastened by haustoria to the epidermis 

 of the leaf. ConidiopJioi'cSy as shown at A in the figure, are 

 quickly formed, and from these, ovoid, unicellular conidia — 

 spores — are evolved during the summer, and propagate the 

 fungus with the aid of the wind, insects, and other agencies. 

 Later on, pert thee ia, B, not so large as the smallest pin's 

 heady having several filamentary or thread-like attachments, 

 are formed upon the mycelium. These are light-coloured 

 at first, gradually becoming black. Within these cases are 

 several smaller cases, asel (C), containing six to eight spores. 

 They do not come to maturity until the early spring, when 

 the cases burst and the spores are distributed. The 

 peritheeia may be upon the plants, or they may fall to the 

 ground, or they may be carried upon decayed leaves. Their 

 preservation during the winter, and the evolution of the 

 spores in the spring, depend upon weather influences, the 

 situation of hibernation, and many other conditions ; while 

 their distribution after safe evolution, especially of those 

 upon the ground, is by no means certain, and, fortunately, 

 depends much upon circumstances. Unless there were 

 many chances against the preservation and distribution of 

 this fungus, as well as of many other injurious fungi, the 

 consequence would be ruinous to cultivators. 



In America strawberry growers sometimes mow the straw- 

 berry plants that are infected by other fungi, such as the 

 Sphcerella fragaria^ for instance, directly after the crop has 

 been gathered, and carry the leaves away and burn them. 

 In other cases the straw or litter put under the plants is set 

 on fire and the leaves burned off. There may be some 

 risk of killing or injuring the plants by this heroic treat- 

 ment ; but it has been adopted in bad cases in this countr}^ 

 It would be well to brush off the leaves of plants infected by 

 Sphcerotheca pannosa as closely as possible without injuring 

 the crowns, and to rake up and burn at once all the leaves 

 and rubbish between the rows of plants. The ground 

 between the rows should be well forked and hoed in the 

 autumn and early spring, to bury the peritheeia^ and weeds 



