Thallus Development in Herpomyces Paranensis (Laboulbeniales)

Abstract

Probably the most distinctive characteristic of Herpomyces paranensis Thaxter is the slender, flexuous prolongation of the uppermost cell of the primary axis of the female thallus. Thaxter (1902) re? ported that the terminal cell of the male is similarly developed; the irregular arrangement of the cells in his drawing of a male (1908), how? ever, suggested that a misinterpretation of the structure of the thallus might have been made. The mature female thallus consists of 2 series of 3-spined perithecia; each series is joined by a short branch to the primary axis. The broad, straight shield of the initial perithecium of each series covers those of subsequently formed perithecia; consequently, the relationships between the perithecia are obscured. Although Thaxter (1908) was able to observe that the perithecial series seemed to result from continued secondary branching, the exact growth pattern of the thallus was not determined. The manner in which the primary axes and the perithecia develop was not indicated. The female thallus differs in 4 significant ways from that of H. stylopygae Spegazzini. In the latter species, each perithecium is pro? duced by a separate outgrowth from the primary axis; a large, curved shield develops; the perithecium has only one spine; and the primary axis bears the persistent spinous spore apex and 2 lateral black holdfasts (Richards and Smith, 1955b). This study of H. paranensis was made for 2 major reasons: first, to determine the form of the primary axes in both sexes and the branching pattern in the female; and secondly, to discover the extent of the similarity between the development of the perithecium and secondary receptacle in H. paranensis and that in H. stylopygae. It is only through careful studies of thallus structure, combined with a knowledge of the interrelationships between host species, that an understanding of the phylogenetic relationships of the species in the genus Herpomyces will be attained. materials and methods