CLASSIFICATION OF FUNGI 59 



directly from the walls and not in asci. The group is 

 very large, and includes a number of species which 

 cause leaf-spot diseases. It also includes several species 

 which cause diseases of roots and twigs. 



The genus Phoma contains many species which are 

 the causes of important diseases. The pycnidia are 

 single, sometimes closely collected, black and sunken in 

 the tissues of the host plant, causing spots with rather 

 indefinite margins. When mature they rupture the 

 epidermis and the spores escape. The conidia are 

 unicellular and colourless. Among the most important 

 are P. betae, Frank, of the beet, P. batatae, E. & H., 

 of the sweet potato, and others which are known to 

 occur in the temperate zones, and probably occur in the 

 tropics. Also P. solani, Hals. , of the potato. 



The species of the genus Phyllosticta are the cause 

 of well-defined spots on living leaves only. The spores 

 are colourless. Among the most important are P. 

 hortorum, Speg., on the egg-plant; P. tabaci, Pass., 

 on tobacco in Italy ; P. bataticola, Ell. and Mart., on 

 sweet potato; P. betae, Oud., on beets; P. coffeicola, 

 Dela., of the coffee ; P. Speschneivii, of the tea. 



In the genus Sphaeropsis the pycnidia are black, 

 spherical, and embedded in the tissues of the host. 

 They finally break through the epidermis, and the 

 spores escape through a small aperture. The spores are 

 ovoid, oblong, unicellular, and dark-coloured. Among 

 the diseases attributed to this genus is a leaf disease of 

 coffee due to an undetermined species. The genus 

 Coniotliyrium contains the species C. coffeae, which has 

 been reported on the coffee. 



In the genus Sphaeronema the pycnidia are mem- 

 branous with long beaks, and are embedded in the 

 tissues of the host. The conidia are ovoid or oblong, 

 unicellular, and almost colourless. In this genus we 

 find S. adiposum, Butler, causing a disease on the 

 stems of the sugar cane ; S. fimbriatum, E. & H. 

 (Sacc.), causing a disease of the sweet potato; and S. 

 album, Fetch, causing a disease on rubber. 



