DISEASES OF PLANTS. 



*7 



certain conditions, not fully known, the mycelium of this fungus 

 grows into minute blackish compact lumps called sclerotia. 

 These bodies remain in a resting condition for some time, and 

 eventually produce fruits resembling in shape a miniature wine- 

 glass, quarter to half an inch high, and of a dark brown colour. 

 This form of fruit is produced in the spring, and its spores give 

 origin to the summer, or Botrytis form of the disease. If the 

 mould shows itself, the plants should be sprayed at intervals of 

 ten days with a solution of potassium sulphide, and in cases 

 where it is known that the disease has previously existed, the 



Fig. 4. — Velvety Mould (Sclcrotinia Fuckeliana). 



(1) Appearance of the summer form of the disease on a portion of a vine leaf ; half 

 natural size (2) Fruit of summer form ; natural size. (3) Fruit of summer form ; highly 

 magnified. (4) Winter fruit ; (A) sclerotium, from which too small stalked cups spring ; 

 (B) one-quarter natural size. (5) Spores of winter fruit ; highly magnified. 



vines should be sprayed, only before the leaf-buds begin to 

 expand, with a solution of sulphate of iron. As a matter of 

 course all diseased leaves that have fallen should be collected 

 and burned ; and every trace of the mould, as it appears on 

 dying parts of plants should be destroyed. It is useless picking 

 off a diseased leaf or twig, rubbing it to powder between the 

 fingers, and throwing it down, on the supposition that the 

 fungus is destroyed ; this is not the case, the very minute spores 

 are only spread about by this method. 



