164 MYCOLOGY 



on definite conidiospores. Of the ten genera of the family, the 

 genera Valsa and Diaporlhe are the most important. Both genera 

 include about 400 species, which are most saprophytic in wood and the 

 bark of woody plants. Valsa oxystoma is the cause of the disease and 

 death of the branches of Alnus viridis in alpine regions; Diaporthe 

 farinosa grows on the branches of the linden, Tilia americana in North 

 America and £>. eucalypti on Eucalyptus globulus in California. 



Family 7. Melogrammatace^. — The stroma are mostly like those 

 of the genus Valsa and rarely like those in Diatrype. They are hemis- 

 pheric and are formed beneath the bark and later break through to the 

 surface, where they are more or less isolated. The perithecia are 

 imbedded in the stroma. Conidial fructifications are formed on the 

 surface of young stroma, or pycnidiospores are produced in pycnidia. 

 The most important genus of this family is Endothia, which is repre- 

 sented by the Chestnut-blight fungus E. parasitica, which lives in the 

 cambium and inner bark of chestnut trees causing a final girdling of 

 the branch and the death of the part beyond the girdled area. It has 

 caused untold injury to the forest groves of America, where the chest- 

 nut tree abounds, and its morphology and its ravages will be described 

 subsequently. 



Family 8. XYLARiACE.ffi. — The stroma of these fungi is developed 

 strongly and is frequently upright and branched. The perithecia 

 are borne in the branched club-shaped portions of the fruit bodies. 

 Early in their growth the surface is covered with conidiospores. The 

 ascospores are unicellular and blackish-brown. The genus Num- 

 mularia, which includes forty species, is represented typically by 

 N. Bullardi, which causes black charcoal-like eruptions on thick 

 branches of the beech, Fagus. Ustulina, with nine species, includes 

 U. vulgaris found on old stems of broad-leaved trees and Hypoxylon 

 with about 200 species is confined mostly to damp wood and old 

 tree stumps. Xylaria digitata, one of the 200 species of that genus, 

 grows on old wood, and X. polymorpha on old tree stumps. This 

 family completes the list of pyrenocarpous fungi. 



Suborder F. Discomycetiineas.— The discomycetous fungi have a 

 filamentous mycelium. Reproduction is by the union of two hyphal 

 branches either of similar size, or differentiated into oogonia and anthe- 

 ridia. The fertilized egg cell either develops directly into an ascus, 

 or it develops ascogenous hyphse from which the asci are formed. 



