284 CLASS ASCOMYCETEAE 



Family Xylariaceae. Because of the similarity of ascus and asco- 

 spore structure in the Xylariaceae and in Anthostoma of the Allanto- 

 sphaeriaceae and of some species of RoseUinia in the Sphaeriaceae it has 

 been suggested that a more natural classification would group these two 

 genera with the Xylariaceae. Among the genera undoubtedly belonging 

 here is Hypoxylon with broadly cushion-shaped to almost spherical 

 stroma. In this genus as well as in the following genera the conidial layer 

 is external on the young stromata. A number of species on logs, stumps, 

 branches, etc. Some of these are 1 cm. or more in diameter and may be 

 bright red. Daldinia has large rounded stromata with pronounced con- 

 centric zones visible in vertical section. The fungus grows on dead trunks 

 and branches and sometimes reaches a diameter of 3 or 4 cm. Its color is 

 black, sometimes almost varnished in appearance. Daldinia concentrica 

 (Fr.) Ces. & De Not. shows excellently the distribution of the ascospores. 

 These are sometimes expelled from the ostioles to a distance of several 

 millimeters. Near large specimens of this species the dead limbs may be 

 blackened for a distance of 10 cm. or more. In Xylaria the stroma is up- 

 right, slender or stout, simple or branched. X. polymoj'pha (Fr.) Grev. 

 forms thick black clubs usually growing on buried wood. These are 

 5-8 cm. or more tall and 1-2 cm. thick, rounded at the apex and velvety 

 at the base. The interior of the stroma is firm and white, the numerous 

 perithecia forming a distinct layer just beneath the surface. In X. hypo- 

 xylon (Fr.) Grev. the basal and apical portions of the slender, usually 

 more or less forked stroma are sterile. This or a closely related species is 

 parasitic upon the roots of the apple. (Fig. 92 F-I.) 



Family Phyllachoraceae. In the great majority of species making 

 up the subfamily Phyllachorineae, the stroma is endophyllous, frequently 

 well organized and firm only near the leaf surfaces, the mesophyllic 

 stroma consisting of less densely compacted hyphae intermingled with 

 remains of the host cells. Perithecial wall distinct. In some species elon- 

 gated conidia are produced in subepidermal pycnidial cavities (Bessey, 

 1919). In the subfamily Trabutiineae the stroma lies between the cuticle 

 and epidermis and in the Scirrhiineae between the epidermis and the 

 palisade layer. There were over 40 genera and more than 500 species 

 recognized by Theissen and Sydow (1915). All were considered to lack 

 true perithecial walls and therefore to belong to the order Dothideales. 

 In the genus Phyllachora and a number of other genera definite perithecial 

 walls are present (Orton, 1924; Petrak, 1924). This character and the 

 presence of true paraphyses in the vast majority of the species justify 

 placing the family in the Sphaeriales, although some of the smaller genera 

 may still have to be retained in the Dothideales. The greater number of 

 the genera are tropical. Phyllachora graminis (Fr.) Fckl. and other species 

 are very frequent parasites of various grasses in the United States and 



