192 DISEASES OF CULTIVATED PLANTS 



tree, favour the disease, as an imperfect circulation of air 

 results, and the rubbish cannot be removed from under the 

 trees. 



Cooke, M. C., Grevillea, p. n (1880). 

 Spegazzini, Revista Agric. and Veter. La Plata, No. 22, 

 Oct. 1896. 



Massee, Kew Bull.) 1909. 



Puttemans, Bull. Soc. Myc. France^ 20, p. 157 (1904). 



HYPOMYCES (FRIES.) 



Perithecia gregarious or crowded on a byssoid stroma, 

 bright coloured, soft, asci 8-spored ; spores elongated, 

 i-septate, hyaline. 



Conidial forms often present. 



Parasitic on various kinds of fungi, perithecia often rosy 

 or red. 



Mushroom disease. Cultivated mushrooms are frequently 

 destroyed in a wholesale manner by Hypomyces perniciosus 

 (Magnus). They are frequently attacked before they break 

 through the soil, and on appearing above-ground are 

 covered with a dense white weft of mycelium. Such mush- 

 rooms rarely increase in size, but rot and decay. The 

 mycelium of the parasite grows along with that of the 

 mushroom from the first, and when the latter is not destroyed 

 in the early stage, continues to increase in size as a distorted, 

 shapeless mass, the cap is rarely formed and if it is developed 

 the gills are morbid and irregular. Finally every part decays, 

 forming a deliquescent, evil-smelling mass. Up to the 

 present the conidial form of the fungus has alone been 

 observed, the conidia of which impart a tinge of rose-colour 

 to the mycelium on the rotting mushroom. 



Conidial form (Mycogone perniciosus^ Magnus). Mycelium 

 forming a velvety stratum ; conidia solitary on short, lateral 

 branches, more or less pear-shaped, i -septate, almost colour- 

 less under the microscope, upper cell almost globose, 

 minutely warted, much larger than the lower, smooth cell, 

 17-22 X9-I2 p. 



A Verticillium stage is also said to be present. When the 

 disease appears, the entire bed as a rule becomes infected. 

 In such cases the spores are present in the soil and dung, 



