286 



COMPARATIVE MORPHOLOGY OF FUNGI 



hyaline ectostromatic cushion just beneath the periderm. The amount 

 of this tissue formed varies widely. When a well-developed ectostroma is 

 formed, pycnidia are formed within it. If this tissue is much reduced 

 it remains sterile and, unless pycnia are formed in the entostroma, only 

 perithecia are produced. At about the time the ectostroma ruptures 

 the periderm, its tissues are colored yellow becoming a reddish orange. 

 The perithecial initials are formed within the bark cortex beneath the 

 ectostroma. Along with the development of the perithecia, there is 

 production of entostromatic mycelium. This may be so vigorous that 



a large stromatic mass containing 

 only the remnants of the bark cells 

 is pushed up through the periderm. 



In these larger stromata the ecto- 

 stroma can no longer be distinguished 

 (P. J. Anderson, 1913). This species 

 has done much damage to Castanea in 

 the United States and Eastern Asia 

 (Shear, Stevens and Tiller, 1917). 

 Endothia gyrosa and E. singularis 

 show a great growth of entostroma, 

 resulting in a large crumbly mass of 

 fungus tissue in which only the rem- 

 nants of the bark cells may be found. 

 This genus must have arisen as a 

 divergent line from some ancestor 

 of Valsa and Leucostoma rather than 

 directly from the latter. 



Xylariaceae. — The haplostroma- 



tic type is most marked in the last 



family (Tavel, 1892; Theissen, 1909). 



186.— Endothia parasitica, l. Sec- rp^e smip i er genera, as Nummularia, 



tion of pycnium. 2. Section of perithecial ,. *^ t , x x1 t^:_j.__- 



stroma. (After Heald, 1913.) 



«*Sitt$x 



mmmlr 



Fig. 



are directly connected to the Diatry- 

 paceae and Diaporthaceae. They 

 form round, discoid, generally amorphous, crustose black stromata, as N. 

 Bulliardi on beech branches. Their mycelia in cultures have branched, 

 fibrous conidiophores with heads of colorless spores. In the interior of 

 the young hypophloedal stroma, there arises in a simple cavity, a flat 

 conidial hymenium which cuts off similar conidia. The outer layer of 

 the stroma covering it is pushed off with the periderm of the twig, so that 

 at maturity the stromata of the perithecia lie free on the surface. 



In the other genera, the stromata develop wholly on the surface 

 of the substrate but as in Ustulina, are indefinite in form. U. vulgaris 

 covers the surface of old trunks and stems of frondose woods with often 

 gigantic, undulating black crusts which in youth are soft and covered by 



