228 DISEASES OF CULTIVATED PLANTS 



Wilt disease of Cotton, Water-melon, and Cowpea. Dr. 

 Erwin F. Smith has described a disease of cotton (Gossypium 

 herbaceum and G. Barbadense), water-melon (Citrullus 

 vulgaris\ and on cowpea ( Vigna sinensis\ caused by a very 

 remarkable and novel type of fungus, which he has named 

 Neocosmopora vasinfecta. The fungus lives from year to year 

 in the ground, and infection always takes place underground. 

 The mycelium forms dense masses in the water ducts, and 

 afterwards invading the parenchyma, by this means the 

 plant is deprived of water and food supplied by the root, and 

 the plant exhibits the disease known as * wilt ' or ' blight.' In 

 this way whole fields of melon and cotton plants are destroyed. 

 The fungus has two conidial forms of fruit. Microconidia 

 produced in the interior of the plant before it is dead. 

 Macroconidia formed on the surface of the host after it has 

 been killed. Ascigerous form of fruit, on dead roots, rarely 

 on the parts above ground. 



Ascigerous stage. Perithecia gregarious, ovate; red, re- 

 sembling those of a Nectria. Asci cylindrical, containing 8 

 uniseriate spores; spores globose or broadly elliptical, at 

 maturity light brown, epispore thickish, wrinkled, 10-12 p 

 diam., or 8-12 X 11-14 /*. 



Microconidia. Produced on the ends of short branches of 

 mycelium in the water ducts and living parts of the stem ; 

 elliptical, continuous, hyaline, 4-25 x 2-6 p. 



Macroconidia (Fusarium stage). Lunulate, 3-5-septate, 

 30-50X4-6 p. On surface of dead stems on sporodochia, 

 which are pinkish or salmon colour. 



A difficult disease to combat, as the infection is in the 

 soil ; as every diseased plant has numerous spores in and on 

 its substance, unless these are destroyed the disease is certain 

 to be conveyed from one place to another. 



Smith, Erwin F., U.S. Dept. Agric., Division Veg. PhysioL 

 and Pathol., Bull No. 17 (1899). 



ROSELLINIA (DE NOT.) 



Perithecia almost superficial, subglobose, papillate, sub- 

 carbonaceous, black, glabrous or hairy, or seated on a velvety 

 byssus ; asci 8-spored ; spores continuous, broadly ovate or 

 elongated and cymbiform, brown, with or without hyaline 

 appendages ; paraphyses present. 



