228 THE ASCOMYCETES 



Usually the ectostroma is deciduous and may bear the conidial 

 stage. When it is thrown off, the entostroma is exposed. The 

 perithecia are sunken in the entostroma, the ostiolar necks ex- 

 tending to the surface. The ostioles may be separate or may 

 open collectively into a few passages. The stromata are cushion- 

 shaped or even broadly effuse. In some species the substratum 

 is not greatly modified in the formation of the entostroma, and 

 its periphery is indicated by a definite dark line. 



Diatrype and Diatrvpella are the most commonly encountered 

 representatives of this family. They differ mainly in that Dia- 

 trype has eight-spored asci, whereas the asci of Diatrypella are 

 polysporous. Acquaintance with this family and its relationship 

 with the Diaporthaceae may be gained from the work of Weh- 

 meyer (1926, 1933, 1941). 



Xylariaceae. The stromata of Xylariaceae are well developed 

 and are entirely fungal in composition. They are nearly always 

 exposed from the beginning and in youth are covered by a conid- 

 ial layer. The stromata are cushion-shaped or crustose in such 

 representative genera as Hypoxylon and Daldinia but are erect 

 and club-shaped or variously branched in Xylaria. 



Nearly all are saprophytic on woody substrata. A few, how- 

 ever, cause important diseases of trees, notably Xylaria mali^ 

 which produces a black root-rot disease of apples [Fromme 

 (1928)] and Nimnmilaria discreta, which causes apple-tree 

 canker [Cooper (1917)]. 



Hypoxylon, with broadly effuse to hemispherical stromata, is 

 the largest genus, containing over 200 species. Daldinia, mono- 

 graphed by Child (1932), has concentrically zonate stromata that 

 may be 3 to 5 cm In diameter. Niinnmdavia discreta forms stro- 

 matic cushions 3 to 6 mm across, which are seated on the wood 

 but protrude through the bark. When the stromata break away, 

 a black ring remains in the wood. Xylaria polymorpha forms 

 thick, black clubs 6 to 8 cm tall, and X. hypoxylon forms stag- 

 horn-shaped stromata 3 to 4 cm tall. 



Little is known about the development of any members of this 

 family, although the grosser features of X. polymorpha and X. 

 hypoxylon were studied by Fisch as long ago as 1882 [Brown 

 (1913)]. Xylaria tentaciilata was found by Brown (1913) to be 

 parthenogenetic. Ascogonial coils form in the young stromata, 



