Genus Hypoxylon
Key to Taxa of Hypoxylon
Accepted Taxa
List of Names

Yu-Ming Ju
Michael J. Adams

Ascal apical rings of Hypoxylon, when present, are exclusively discoid, i.e., with the diameters greater than the heights. There are a few taxa lacking or having highly reduced apical rings. These taxa are compared in NOTES on H. commutatum. They do not appear to be closely related, and raise the possibility that ascal apical rings might have disappeared independently in different lineages of Hypoxylon. Ascus rings of most taxa blue in Melzer's reagent, i.e., are positive. The amyloidity is positive in most specimens of those taxa where ascal apical rings exist. Nonetheless, rings with a negative reaction are encountered in various taxa. Different collections of certain species show different iodine reactions. Hypoxylon cohaerens sometimes has inamyloid rings (Parker and Reid, 1969), as does H. stygium. Caution should be exercised in determining whether apical rings of a specimen do not stain or are actually absent. Ascal stipe length is variable in many taxa. However, when the stipes are very long, as in H. begae, H. haematostroma, and H. polyporum, they appear to be diagnostically useful.