DEMATIACEAE S91 



conidia. In the other type the reproductive hyphae form an 

 arachnoid weft at the surface of the lesion, and the conidia are 

 abstricted from short laterally formed conidiophores that stand 

 singly. In the first group is Alycosphaerella vwri {Cercosporella 

 uiaciilans), occurring on mulberry. In the second group are 

 Ravmlaria areola on cotton and Cercosporella persicae on peach, 

 which produce diseases commonly called frosty milde\v. The 

 perfect stage of each has been determined to be Alycosphaerella. 

 In Piricularia are species having simple or branched conidiophores 

 bearing ovoid to pear-shaped, septate conidia. Piricularia oryzae 

 is wide-spread on the foliage of rice. Piricularia grisea is com- 

 mon on pasture and hay grasses. 



Dematiaceae. Cladosporium is encountered by all ^\'orkers 

 who attempt to isolate fungi in culture. Its branched conidio- 

 phores bear chains of acrogenously produced conidia, single- 

 celled or two- or three-septate. The genus contains many sapro- 

 phytic species that aid in the decomposition of all sorts of plant 

 tissues and also several that produce disease in plants and ani- 

 mals. Perfect stage connections are unknown. Cladosporiinii 

 jiihinn blights the foliage of greenhouse-grown tomatoes. Peach 

 scab, caused by C. carpophihnn, involves both the fruit and twigs 

 [Keitt (1917)] and is especially destructive to late-maturing va- 

 rieties. It hibernates in twig lesions. Cladosporiinn ciicwuerimnn 

 causes scab on the fruit of cucumber. Several other important 

 plant pathogens have been placed in Cladosporium, for example, 

 C. citri^ but they properly belong in Sphaceloma, which has been 

 established to be genetically connected with Elsinoe, a hemi- 

 sphaeriaceous fungus. 



Chromoblastomycosis in man is caused by an extremely pleo- 

 morphic species, for which a number of generic names, including 

 Hormodendrum, Phialophora, Acrotheca, and Fonsecaea, have 

 been proposed, but it may well be eventually placed in Clado- 

 sporium. 



Serious diseases of cereal crops and wild grasses, called stripe 

 diseases because of the shape of the lesions, are induced by Hel- 

 minthosporium. This genus includes fungi ^\•ith stout, un- 

 branched, septate conidiophores, and with colored, septate, thick- 

 walled, boat-shaped conidia. A few species, such as H. ravenelii, 

 completely envelope the inflorescences and are of such wide- 

 spread occurrence that the hosts are called smut grass. 



