196 THE FUNGI WHICH CAUSE PLANT DISEASE 



Such form genera as Verticillium, Tubercularia, Sphacelia, 

 Sphaerostilbe and Isaria are connected with the Hypocreales. 



The order includes some sixty genera, and over eight hundred 

 species. Of these only a half dozen genera contain important plant 

 parasites, another half dozen genera, parasites of less importance. 

 The rest are saprophytes, insect parasites, etc., of no economic 

 significance. 



Opinion differs as to the characters which should be made the 

 basis for subdivision of this family, whether to throw main stress 

 upon the structure of the perithecium or upon the character of 

 the spores. 



Following Lindau the order contains a single family, Hypo- 

 creaceae,^^"^ which may be divided into six subfamilies. Accord- 

 ing to a more recent treatment of the American members of the 

 group by Seaver " two families and four tribes are recognized. 

 Lindau's tribes Hyponectriese, Hypo'myceteae, and Melanosporese 

 are imited with a part of Nectrieae imder the last name while the 

 remaining genera, referred by Lindau to this tribe, constitute the 

 tribe Creonectrese. These tribes constitute the family Nectriaceae. 

 The remaining tribes, Hypocreeae and Clavicipiteae with about the 

 same limits constitute the family Hypocreaceae. 



Key to Tbibes of Hypocreacese 



Perithecia at first sunken in the substratum, 



later erumpent 1. Hyponectriese. 



Perithecia not sunken in the substratum; 

 stroma present or absent 

 Stroma cottony, never fleshy; perithecia 

 immersed in the stroma, or borne on 



its surface 2. Hypomycetese. 



Stroma fleshy or wanting 

 Spores dark colored; perithecia free on 

 the substratum (in some species 

 of Melanospora with a cottony 



stroma) scattered 3. Melanosporete. 



Spores hyaline, yellow or red 

 Perithecia without a stroma, or on a 



fleshy stroma 4. Nectriese, p. 197. 



