Fungi 



201 



ing gray, brick-red, or brownish tints. Nummularia is common on 

 dead branches of beech, elm, oak, locust, and other trees. It is gen- 

 erally flat, orbicular, or elliptical in form. Ustilina is a crustaceous 

 form, rather diffuse and irregular in shape. It is most common 

 on the roots of rotten stumps. Hypoxylon is more or less globose 

 in form, and the color is brick-red, brown, or black. It is found on 

 dead twigs and bark of various trees, especially beech, and is more 

 abundant in moist situations. Xylaria (Fig. 55) is found on decaying 

 stumps and logs, and often apparently on the ground, but really 

 growing on twigs, wood, 

 and bark just under the 

 surface. When mature it 

 is black outside and white 

 or light-colored within. 

 When young, it is easily 

 cut in paraffin; in some 

 forms the ascospores are 

 fully formed before the 

 stroma becomes hard 

 enough to occasion any 

 difficulty in cutting. When 

 the stroma becomes black, 

 many members of the 

 Xylariaceae become very 

 hard and brittle, so that 

 sections are likely to be 



unsatisfactory. For general morphological study it is better to 

 break the stroma transversely and examine with the naked eye 

 and with a pocket lens. The asci with their spores can be teased 

 out and mounted in water. For permanent preparations, soak 

 the stroma for a month in equal parts of 95 per cent alcohol 

 and glycerin; then cut sections, and, after leaving them in glycerin 

 for a day or two, mount in glycerin jelly. It is better not to stain 

 the old stages (Fig. 55). For illustrative purposes, select forms 

 which can be cut in paraffin. The method just given merely shows 

 that such material can be cut. 



B 



FIG. 55. Xylaria: A, transverse section of 

 young stroma showing perithecia; X8, B, two 

 asci with ascospores. X245. 



