278 



MONOGRAPH OF THE LABOULBENIACEiE. 



PEYRITSCHIELLA Thaxter. Plate VI, figs. 7-24 ; Plate II, fig. 12. 



Proc. Am. Acad. Arts and Sci. Vol. XXIV, p. 8, 1890. 



Receptacle composed of four superposed areas : a basal consisting of a single cell ; a sub- 

 basal consisting of a single cell or of several cells transversely and asymmetrically disposed in 

 a single row, one or more of wbich may be appendiculate ; a sub-terminal area consisting of a 

 similar series of several cells appendiculate at eitber side, and, on one side only, producing tbe 

 single antberidium ; and, lastly, a terminal series like tbe sub-terminal, but bearing one, rarely 

 two, perithecia centrally placed ; the cells of the series external to the perithecia, and the cell be- 

 tween them, if there are two, appendiculate. Antheridium conical, compound, forming a sharp, 

 tooth-like projection on one side. Appendages simple, continuous, separated from tbe cell which 

 bears them by a prominently constricted, usually blackened septum. Spores once septate. Peri- 

 thecia symmetrical or nearly so, the tips ending in four papillae. 



This, together with the following and very nearly related genus Dichomyces, constitutes a 

 peculiarly well marked type among the Laboulbeniacca?, and no other form possessing a com- 

 pound antheridium, with the exception of Dimorphomyces, presents the same tendency towards 

 the production of a bilaterally symmetrical receptacle, which is so perfectly developed in 

 Dichomyces. In the present genus, there is always an irregularity in the form, and an asym- 

 metry in the disposition of the cells, especially in the two lower transverse series ; and though in 

 P. geminata a greater degree of symmetry is attained than in any other species, the lower 

 series is always asymmetrical, and in all cases only a single antheridium is ever found. 



The development of the receptacle is comparatively simple. The germinating spore, as in 

 fig. 11, develops a terminal appendage which corresponds to the appendage lying at the left 

 of the perithecium in figs. 8 and 10, or between the two perithecia in fig. 7. The larger, lower 

 segment of the spore then divides into four cells, by the formation of three septa (fig. 12). The 

 lower of tbese, the basal cell of the receptacle, undergoes no further modification, and in the 

 single species P. curvata, the sub-basal cell remains unchanged. In all the other species, how- 

 ever, the sub-basal cell and the two cells above it become divided in a characteristic fashion. 

 This division is effected by the formation of oblique septa cutting off the two upper angles of 

 the cell, as in fig. 13. The small triangular cells thus formed begin to grow obliquely outward 

 and upward, as seen at the right in fig. 13, and through the formation of further oblique 

 divisions in these cells the characteristic transverse series result (fig. 14). The number and 

 position of the appendages varies in different species and in different individuals, as indicated 

 by the figures, and are quite peculiar in structure and appearance. They are simple and con- 

 tinuous, or sometimes pseudoseptate, and always connected with the cell that bears them by a 

 characteristically constricted, usually blackened septum. They vary in shape from a mere blad- 

 der-like oval cell (fig. 20, Plate VI) to a more highly developed form, such as occurs in P. cur- 

 vata (fig. 9). The appendages of the following genus, Dichomyces, are similar in all respects ; 

 bat in no other case, with the exception of the species of Chitonomyces and its nearest allies 

 do appendages occur having a similar appearance. 



A single antheridium only is produced on one side from the sub-terminal member of the 

 superposed cell-series'. Their structure corresponds very closely to that of Dimorphomyces, ex- 



