262 COMPARATIVE MORPHOLOGY OF FUNGI 



Sphaeriales, i.e., they are leathery, woody or carbonaceous and generally 

 fragile. Next will be discussed a group of families in which the peri- 

 thecia are formed on the surface of either the substrate or the stroma. Of 

 the group on the surface of either the substrate, are the Sphaeriaceae and 

 Ceratostomataceae ; in the former the perithecial opening is generally 

 short, papilliform, in the latter it is long necked or even drawn out like 

 a hair. 



Sphaeriaceae. — This family is divided into two tribes, the Tricho- 

 sphaerieae (perithecia covered with hair on the whole surface or at 

 least at the base) and the Melanommeae (perithecia smooth). There 

 are more than one thousand species, generally saprophytic on wood, 

 bark, tree trunks, etc., more rarely parasitic. They cover large stretches 

 of the substrate with a turf, causing it to appear as if gunpowder were 

 scattered over it. The only genus of economic significance is Rosellinia, 

 whose hairy (as in the Trichosphaerieae) or naked (as in the Melanom- 

 meae) fructifications occur both singly and gregariously, and are also 

 gregariously immersed in a loose hyphal felt; in the saprophytic forms they 

 often seem like those of the Sordariaceae. Rosellinia necatrix is a very 

 dangerous parasite on roots of the vine and pleached trees. As those of 

 many other subterranean fungi, its rhizomorphs — white in the vegetative 

 stage or brown in age — penetrate the interior of the root, kill it and live 

 on it saprophytically (Dematophora form). In this condition, on black 

 sclerotial hyphal knots they form their brown conidiophores which cut off 

 hyaline conidia on their ultimate branches. In the course of the year, 

 they form the perithecia on the rotting roots (Prillieux, 1904). These 

 are hard and carbonaceous; at maturity the paraphyses and the ascus 

 wall gelify, the perithecial papilla is thrown off like a stopper by the 

 tearing of a dehiscence zone and the brownish black ascospores exude 

 in a drop of slime. R. quercina is known as a root disease of oaks; another 

 species, as the gray root fungus of the Javan cinchona plantations; the 

 former forms massive black sclerotia, the latter chiefly Graphium coremia. 



Ceratostomataceae. — This family is best known as a saprophyte on 

 the woody parts of plants, economically important as the cause of sap 

 stains, bluish discolorations of lumber which do not greatly alter the 

 strength of the timber. Two common species, Ceratostomella pilifera 

 and C. echinella, have the form genus Graphium as an imperfect stage. 

 C. fimbriata, the cause of black rot of the sweet potato, has an imperfect 

 stage formerly known as Sphaeronema fimbriatum. There seems a 

 slight suggestion of heterothallism since antheridia and ascogonia 

 arise from separate hyphal strands. The antheridium coils about the 

 ascogonium, which is differentiated in a basal cell, ascogonium and tricho- 

 gyne, the latter continuous with the ascogonium. The trichogyne may 

 fuse at any point it comes in contact with the antheridium, the single 

 male nucleus migrates into the ascogonium and fuses with the female 



