260 DISEASES OF CULTIVATED PLANTS 



Willow branch blotch. Large, black, blister-like patches 

 varying from i-io cm. long are formed on the branches of 

 different kinds of willow, by Cryptomyces aureus (Mass.) The 

 margin of the patch is well defined and often lobed, and at 

 maturity the black upper surface breaks away from the sur- 

 rounding bark and often falls off. 



Spores arranged in one row in the ascus, elliptical, 

 colourless, then yellowish, 20-25X10-12 //,. Spermogonia 

 are produced in special receptacles in the stroma, containing 

 minute ovate spermatia about 5 /* long. 



SCLEROTINIA (FCKL.) 



Ascophore smooth, brown, supported on a long, slender 

 stem, springing from a blackish sclerotium, asci narrowly 

 cylindrical, containing 8 spores in a single row, spores elon- 

 gated, hyaline, i-celled. 



In several species a conidial form is known, which may 

 belong to either of the following form-genera, Botrytis^ 

 Monilia, and Oidium. 



Closely allied to Ciboria^ which differs in the ascigerous 

 stage not originating from a sclerotium. 



Many of the species are very destructive parasites. 



Vine Sclerotinia (^Sclerotinia fuckeliana, De Bary) is often 

 the cause of very serious injury to the vine ; every part of the 

 plant is attacked, the leaves and fruit more especially becom- 

 ing covered with a dense, fluffy, mouse-coloured mould, 

 covered with myriads of spores, which become free and float 

 about and infect other portions of the vine. At a later stage 

 small black sclerotia are produced in the substance of the 

 plant at those points that were covered with mould. During 

 the following spring these sclerotia produce either the coni- 

 dial or ascigerous form of fruit, depending on certain condi- 

 tions as to temperature, moisture, etc. Istvanfft states that a 

 continuous rainy period favours the development of the 

 Botrytis condition, especially on sclerotia that have fallen to 

 the ground, or are attached to fallen leaves or fruit. 

 Sclerotia that remain attached to living branches often pro- 

 duce the ascophore form of fruit in the spring, and the 

 spores escaping from such fruits are capable of infecting the 



