MONOGRAPH OF THE LAP.OULBENIACEvE. 



3G3 



the conspicuous prolongation of its receptacle beyond the base of the perithecium, which gives 

 it a more or less furcate habit. The perithecium is large and its stalk-cell more highly devel- 

 oped than that of any other species. 



Rhachomyces Lathrobii Thaxtcr. Plate X, figs. 22-23. 



Proc. Am. Acad. Arts and Sci. Vol. XXX, p. 467; Acanthoinyces Lalhrobii Thaxterl. c. Vol. XXVIII, p. 178. 



Perithecium becoming slightly suffused with brown, its blunt conical tip dark brown, con- 

 trasting ; rather slender, slightly inflated towards the base, borne on a short stalk-cell more or 

 less concealed. Receptacle consisting usually of eight to ten superposed cells, forming the main 

 axis and deeply suffused with blackish brown except at the nearly hyaline septa. Appendages 

 large, curved, almost opaque, nearly equalling, often greatly exceeding, the tip of the perithecium. 

 Spores about 50 x 4/*. Perithecia, 100-130 x 35-40 /x. Appendages (longer), 150-450 /x. Re- 

 ceptacle (average), 110 /j, long. 



On abdomen of Lathrobium longiusculum Grav., New Hampshire and Lake Superior; 

 Lathrobium sp., Pennsylvania. 



The appendages of the specimens from New Hampshire are constantly far longer than those 

 of the Lake Superior specimens, resembling A. pilosellus in this respect. The two forms seem 

 otherwise identical, and are distinguished from A. pilosellus by the characteristically brown-tipped 

 perithecium, longer receptacle, and more densely crowded appendages. The infested hosts were 

 all found in the collection of the Museum at Cambridge. 



Rhachomyces pilosellus Thaxter. Plate XII, figs. 12-15. 



Proc. Am. Acad. Arts and Sci. Vol. XXX, p. 467; Laboulbenia piloseila Robin, Traite' du Microscope, p. 912, fig. 285 (1871); 

 Acanthomyces brevipes Thaxter, Proc. Am. Acad. Arts and Sci. Vol. XXVIII, p. 177. 



Perithecium suffused with reddish brown, subfusiform with a distinct stout stalk-cell. 

 Receptacle very short, the main axis consisting usually of five superposed cells, with a short pro- 

 longation beyond the base of the perithecium, normally of not more than three or four cells, the 

 cells all pale yellowish or with brown suffusions, the septa in all cases usually hyaline. Append- 

 ages few in number, opaque or nearly so, scattered, some of them very long, curved, and 

 greatly exceeding the tip of the receptacle. Spores, 55 x4/i. Perithecium, 150-165 x 45-55 ft. 

 Receptacle, main body about 75 x 30 its prolongation about 35-40 n. Stalk of perithecium 

 about 40 x 30 /a. Appendages (longest), 375-500 p. 



On Lathrobium fulvipenne Grav., Germany. 



This small species is distinguished from its near ally R. Lathrobii, by its shorter and 

 differently shaped receptacle, concolorous perithecium, and scattered appendages. The specimens 

 examined were obtained from material of its host in the collection of the Museum at Cambridge 

 labelled " Germany," and were found growing on the insect's abdomen. I have been unable to 

 discover any diagnosis of this species in Robin's " Traite " beyond the description of the plate, 

 and was unaware that no description existed when I referred my own species to this form in the 

 paper cited above. Although the name R. brevipes might very properly be retained, in view of 



