262 



THAXTER. — MONOGRAPH OF THE LABOULBENIACE^E. 



This aquatic genus forms a very perfect link between the closely allied aquatic genus Chitonomyces 

 and the terrestrial genera Peyntschiella and Dichomyces. The antheridium, unlike that of Chitonomyces, 

 is inserted laterally, like that of Peyritschiella, although in a different relation to the perithecium, and 

 its character can readily be determined. The regular arrangement of the cells of the receptacle in tiers 

 recalls very strongly the conditions in the terrestrial genera just mentioned, although the perithecium 

 comes to be related to the receptacle as it is in Chitonomyces, the marginal portion, as in this genus, being 

 terminated by a similar characteristic, bell-shaped cell. Both the species occur in North America on 

 large water beetles, Hydrophilida?. 



Limnaiomyces Tropisterni Thaxter. Plate XXXIV, figs. 14-15. 

 Proc. Am. Acad. Arts and Sci., Vol. XXXV, p. 428. April, 1900. 



Perithecium amber-brown, straight, erect, with a slight nearly median inflation, or tapering but very 

 slightly to the undifferentiated tip; the upper half free. Receptacle pale straw-colored, distally dull 

 amber-brownish, the foot minute, black; the basal cell short and small, the lower tier consisting of two 

 cells which are nearly equal, several times as long as broad: the second tier consisting of three cells, the 

 posterior one longest, the median longer than the anterior, which terminates in the antheridium, which 

 is subtended by four basal cells, two of them outer and lower and separated by oblique partitions, while 

 a smaller upper one lies on either side: above the antheridium two vertically elongated cells form the 

 clearly defined base of the perithecium; external to these cells, and somewhat obliquely separated from 

 them, lies the broad base of the inner marginal cell of the distal portion of the receptacle, which lies next 

 above the middle cell of the upper tier, its cavity nearly obliterated above as the spores mature, the pri- 

 mary appendiculate cell which terminates it rather elongate; the proliferation of the outer marginal 

 cell beginning quite near its base, forming a series of about eight cells separated by oblique septa and 

 terminated by small appendiculate cells; the appendages very small, vesicular, brownish below. Peri- 

 thecia 127-175 X 35-37 y. Receptacle, distal part 75-110 y. Appendages 6 X 3 y. Total length to 

 tip of perithecium 240-375 y, to tip of receptacle 190-265 y. 



On Tropisternus sp. indet., Paris Museum, No. 47. Mexico. On tip of abdomen. 



This species is conspicuous from its large size and dark brown color, and is readily seen projecting 

 from the tip of its host's abdomen. That it has been observed only once on specimens in alcohol in the 

 Paris Museum, may perhaps be accounted for by the fact that it appears to be very readily detached, 

 and grows in an exposed situation. In any ease it has been sought for in vain on the very numerous 

 Central and South American Tropisterni that have been subsequently examined. 



Limnaiomyces Hydrocharis Thaxter. Plate XXXIV, figs. 10-18. 

 Proc. Am. Acad. Arts and Sci., Vol. XXXV, p. 429. April, 1900. 



Hyaline. Perithecium rather stout and short, somewhat inflated, its tip abruptly bent outward, 

 the apex bluntly rounded or nearly truncate; the tip and the appendiculate cell usually symmetrically 

 divergent. Basal portion of the receptacle relatively short and stout but otherwise similar in structure 

 to that of L. Tropisterni; the two basal cells of the perithecium almost obliterated at maturity so that 

 its base appears to rest immediately on the antheridium; the distal portion of the receptacle bordering 

 the perithecium to its tip, the inner cell becoming almost wholly obliterated in the middle and terminat- 

 ing in a short bell-shaped appendiculate cell which is slightly divergent: the outer marginal cell usually 

 proliferating three times; of the three cells thus formed the two inner, as a rule, produce well developed, 

 long, simple, hyaline appendages; not, however, as well developed as the primary appendage, which may 

 be twice as long as the perithecium. Spores 50 X 3 y. Perithecia 60-80 X 17-20 y. Receptacle, 

 basal part, 50. X 20-26 y, distal part 50-62 y. Appendages, longest, primary 140 y, secondary 70 y. 

 Total length to tip of perithecium 100-128 y. 



At tip of abdomen of Hydrocharis obtusatus Say, Cutts Island, Kittery Point, Maine. 



Unlike the preceding species the present form, being small and pale, is seen with great difficulty, 



