:Xylariaceae: Biscogniauxia

DEVELOPMENTAL ASPECTS

The fullest accounts of development in Biscogniauxia are those of the Tulasne brothers (1863) [as Nummularia]. Rogers (1967c) elucidated the developmental cytology of ascospores of Biscogniauxia grenadensis (J. H. Miller) Whalley & Laessøe var. macrospora (J. H. Miller) Whalley & Laessøe [as Hypoxylon]. Ascospores are initially uninucleate. Most frequently, one mitosis occurs; one of the two resulting nuclei is cut off in a cellular appendage. In some cases the nucleus in the spore body divides again, one of the nuclei becoming located in the end of the spore body opposite the appendage. In a few instances no appendage is formed and the spore body matures in a bi- or trinucleate condition. Most ascospores have a mature brown body cell and an appendage in which the nucleus disintegrates. Frequently, the appendage dehisces, resulting in a brown ascospore with a conspicuously truncate end. Cytological phenomena are similar in B. anceps (Sacc.) J. D. Rogers, Y.-M. Ju, & Cand. (Rogers et al., 1996). In that species, however, both the body cell and the appendage cell of most ascospores remain hyaline and both can germinate. The evolutionary implications of these observations are discussed later.

Ju and Rogers (1996) have discussed the gross anatomy of Biscogniauxia stromata. Perithecia are usually contained within individual carbonaceous locules. They are usually easily removable as individual sacs, a feature commonly seen in Camillea and Rosellinia, but observed much less frequently in Hypoxylon, Daldinia, and most other xylariaceous genera. Large perithecia (0.3 mm diam or above) of most taxa communicate with the external environment by individual ostiolar canals. Smaller perithecia (less than 0.3 mm diam) often have communal ostiolar canals shared by two or more perithecia. A species newly described herein, B. communapertura Y.-M. Ju & J. D. Rogers, produces numerous perithecia in rosettes, each rosette having a single ostiole. One becomes aware of this by observing that the stromatal surface features a relatively few scattered ostioles for a large number of small perithecia. Taxa in the related genus, Camillea, much more frequently show shared ostiolar canals. We consider it to be a relatively advanced feature.