240 



THAXTER. MONOGRAPH OF THE LABOULBENIACE^E. 



LABOULBENIINEjE. 



Antheridia consisting of specially differentiated cells or group of cells. 



PEYRITSCHIELLACEiE. 



Genera monoecious or dioecious, the antheridia "compound," the antheridial cells originally and 

 at maturity (except in Distichomyces) opening into a common cavity whence they discharge their sperm- 

 cells through a common pore. 



DIMORPHOMYCES Thaxter. 



This well marked dioecious genus was founded on two New England species, D. injectus and D. 

 denticulatus, and as far as these species are concerned I have nothing to add to my original account ex- 

 cept to mention that D. injectus has been observed on a Falagria sent me from Ohio. Both species are 

 no doubt as common elsewhere as they are in New England. The present addition of two species is, 

 in all probability, no reliable index of the numerical importance of the genus, since the hosts appear 

 to be neglected by collectors and are not well represented in the collections examined. The plants them- 

 selves, too, are very minute, pale in color, and visible with great difficulty on dried hosts. 



In comparing the structure of these forms with that which is characteristic of the simpler types of 

 the family, it is evident that there is a close correspondence in essentials. The primary receptacle in 

 both sexes consists of the usual basal and subbasal cells, and its axis is terminated by a simple primary 

 appendage of two or three superposed cells. The male, except in abnormal individuals which rarely 

 occur, produces a single antheridium which arises directly from the subbasal cell. In the female, how- 

 ever, the conditions are much more complicated, since the perithecia arise from lateral branches, 

 "secondary receptacles," derived from the subbasal cell, which are bordered below by an extension or 

 outgrowth of the basal cell that keeps pace with the development of the secondary receptacle. In the 

 two species originally described two of these receptacles arise, one on either side, which are more or 

 less symmetrical. In the two herewith illustrated, however, but one such receptacle is produced and 

 the individuals are asymmetrical in consequence. The cell relations are clearly seen in D. Myrmedonics, 

 Plate XXVIII, fig. 15, in which the actual conditions are more readily made out than in the species 

 first described. A reexamination of the latter leaves no doubt as to the essential correspondence of 

 their structure. 



As far as I have observed, the sexes are always associated in the spore-pairs in this genus, although, 

 as in other dioecious forms, instances may occur in which they fail to be juxtaposed at the point of 

 attachment to the host. 



Dimorphomyces Myrmedoni,e Thaxter. Plate XXVIII, figs. 14-16. 

 Proc. Am. Acad. Arts, and Sci., Vol. XXXV, p. 409. Apr., 1900. 



Male individual tinged with smoky brown, relatively small and stout, the neck of the antheridium 

 short, the primary appendage consisting of three superposed cells, the middle one distinguished by slight 

 constrictions and by dark septa, especially below; the terminal one bluntly rounded distally, twice as 

 long as broad; the thick walls above becoming disorganized. Total length to tip of antheridium, in- 

 cluding foot, 65 fi; to tip of appendage 40 fi. Antheridium 38 /i in length, the center 25 X 14 /z. 



Female individual relatively large, tinged with smoky brown, the primary appendage consisting 

 of three cells; the fertile secondary receptacle developed, almost at right angles to the primary axis, 



