:Xylariaceae: Kretzschmaria

INTRODUCTION

Kretzschmaria Fr. (misspelled as Kretschmaria) was established on Sphaeria clavus Fr.: Fr. (Fries, 1849). The most important part of the diagnosis reads: "Conceptaculum carbonaceum, crassum, rigidum, stipitatum, capitatum, capitulo intus cavo, cellulis rotundatis amplis referti..." Up to the present, the general concept of Kretzschmaria has been much as Fries described it, i.e., a stipitate ascigerous stroma with interior flesh surrounding and beneath perithecia disintegrating. Ustulina Tul. & C. Tul. is based on U. vulgaris Tul. & C. Tul. [= U. deusta (Hoffm.: Fr.) Lind] which features a massive pulvinate stroma that becomes hollow at maturity. Martin (1970) recognized the great resemblance of this species to Kretzschmaria and transferred it as K. deusta (Hoffm.: Fr.) P. Martin. He transferred a number of other taxa to Kretzschmaria, some of which we accept as members of other genera. Martin (1970) recognized the close relationship between Xylaria Hill ex Schrank and Kretzschmaria, separating them on the vertical orientation of perithecia and umbonate or aristate sterile apex on the fertile parts of some species of the latter genus. Interestingly, K. clavus (Fr.: Fr.) Sacc.—the type species of the genus—does not have umbonate stromata (Martin, 1970).

An important paper supporting the acceptance of Ustulina as congeneric with Kretzschmaria was that of Ko et al. (1982). They believed that Kretzschmaria-like and Ustulina-like stromata represented forms of the same taxon, K. clavus. Their evidence was based on ascospore measurements and colony morphology in agar culture. We have, in fact, reexamined stromata forwarded to JDR by W. H. Ko in 1980. In that case, the kretzschmarioid stromata are those of K. clavus and the ustulinoid stromata are those of K. pavimentosa (Ces.) P. Martin. As can be seen in descriptions of these taxa elsewhere herein, the ascospores are morphologically different and have length ranges that only slightly overlap. One of us (JDR) has repeatedly sought evidence that K. clavus grades into a ustulinoid form, but has found none. On the other hand, as will be discussed later, the culture colony morphologies of both kretzschmarioid and ustulinoid fungi—even some that are strongly dissimilar in the teleomorphic states—are very similar. Indeed, it is cultural features that have greatly influenced our decision to accept Kretzschmaria and Ustulina as morphological manifestations of one genus (but not of one species!).

In this treatment of Kretzschmaria we include taxa with the following characteristics:

1. Stromata that at first bear conidia uniformly overall (ustulinoid taxa) or on coremioid structures (some, perhaps all, kretzschmarioid taxa).

2. Mature stromata that have a carbonaceous outer layer encasing a rather soft white to blackish inner layer. Stromata becoming hollow as perithecia mature, finally forming brittle shells with perithecia attached.

3. Stromata that are attached to the substrate by definite stipes (kretzschmarioid taxa) or by scattered narrow connectives (ustulinoid taxa).

4. Stromata that are devoid of colored pigments in KOH.

5. Anamorph that is xylarioid, more or less assignable to Geniculosporium Chesters & Greenh. Not ordinarily produced in cultures of taxa that have been studied in culture.

6. Ascus rings that are higher than broad, usually massive and bluing in iodine (Melzer’s reagent).

7. Ascospores that are more or less inequilateral with a germ slit on the flatter side. Perispore not dehiscent in KOH.

8. Cultures on 2% Oatmeal Agar (Difco) that soon become furrowed, distorted, and tend to separate from the culture plate.