SCLEROTINIA 273 



into the fruit, and demands an insecticide. Adding Paris 

 green to the Bordeaux mixture should be tried. 



Norton, J. B. S., Plant Diseases in Maryland in 1902. 

 Woronin, Mem. de VAcad. Imp. St. Petersb., Ser. 7, 36. 



Sweet chestnut disease. The leaves and young fruit of 

 the sweet chestnut (Castanea vesca) are often injured to a 

 serious extent by a fungus called Sclerotinia padi, Wor. 

 ( = Stromatinia padi, Wor., and Stromatinia Linhartiana, Prill, 

 and Del.). The leaves are attacked in the spring, and 

 in rainy weather the disease spreads rapidly. The leaf is 

 usually first attacked near the base of the central vein, and the 

 fungus passes upwards following the vein, extending also on 

 each side of the larger lateral veins. The infected portion soon 

 becomes dark brown, eventually the entire leaf becomes 

 brown and dies. A greyish-white delicate powder appears on 

 the dead patches on the upper surface of the leaf, more 

 especially along the lines of the veins. This is the Monilia 

 or conidial form of the fungus. The conidia of the Monilia 

 stage are mostly conveyed by insects to the stigmas of the 

 chestnut flowers, where they germinate, grow down the tissue 

 of the style, and destroy the ovules, forming in the place they 

 would normally have occupied, a sclerotium. Fruits that 

 have been attacked are soon killed, and do not decay, but 

 pass into a compact mummified condition, and fall to the 

 ground, and during the following spring give origin to one or 

 more of the ascigerous fruit under the form of a shallow cup 

 supported on a stout stern. Prillieux has proved by a series 

 of carefully conducted experiments that the spores from the 

 ascigerous fruit will give origin to the Monilia form of fruit 

 on the leaves. 



Ascigerous form. Ascophore cup-shaped, then almost flat, 

 o - 5-i cm. diam., stem i-i'5 cm. long, brown, dingy grey, or 

 with a tinge of violet. Asci cylindrical, 8-spored ; spores 

 elliptic-oblong, colourless, 12X7-7 '5 l l - On mummified fruit 

 on the ground in spring. 



Monilia form. Numerous colourless chains of conidia 

 spring from a compact stromatic base, which bursts through 

 the epidermis. The component conidia when free are more 

 or less lemon-shaped. 



When the leaves become infected, the fruit also suffers to a 

 serious extent, hence it is important that the spring infection 



S 



