1971 PARASITIC FUXGI— STEVENS 31 



DiMERiUM Sacc. and Syd. 



SyU. Fung., 16:410, 190. 



43. DiMERiUM GuiAXENSE Stevens n. sp. 

 [Figures 77, 107] 



Spot irregular in shape showing from both sides of the leaf, to several 

 millimeters in diameter, dead, brown or ashen as seen from above. Superfi- 

 cial mycelium pale straw colored, non-hyphopodiate, non-setose, hypophyl- 

 lous, abundant. Colonies yellow when young black when old. Perithecia 

 superficial, globular, black, 105 to 185m in diameter, smooth, surface cells 

 agglutinated. 



Asci 4-spored, clavate, hyaline, thick walled, 120 x 36/u, evanescent, 

 several in each perithecium, imbedded in a matrix composed of tangled, 

 gelatinous, crooked, filiform paraphyses. Spores yellow to dark brown, 

 long pyriform to elliptical, usually tapering toward one end, 1 to 2 septate, 

 36 to 50 X 14 to 18/1, often truncate at one end. 



On unknown rosaceous host. 



British Guiana: Kartabo, July 24, 1922, 656. 



According to the key of Theissen and Sydow'- this would fall in the 

 genus Dimerium if the spores be regarded as 2-celled; in Perisporina if 

 three-celled but it would be excluded from Perisporina by the absence of 

 mycelial setae also by the presence of paraphyses. It shows many similar- 

 ities with Perisporiopsis P. Henn. as figured by Arnaud'' but differs from 

 that genus in possessing no mycelial setae or paraphyses. Though the 

 spores are frequently 2-septate, I place the present species in the genus 

 Dimerium as an abberant form. 



Mycophaga Stevens n. gen. 



Fungus superficial, perisporiaceous, non-hypopodiate, no setae on 

 mycelium or perithecium; spores hyaline, 3-septate. 



44. Mycophaga guianensis Stevens n. sp. 



Mycelium non-hyphopodiate, honey-yellow, forming a tangled net- 

 work. Perithecia globular, non-ostiolate, 1 23 to 1 38m, no appendages, smooth. 

 Asci 61 to 72 X 18m, conglobate; no paraphyses; spores 3-septate, hyaline, 

 32 to 40 X 3.5m, obtuse, slightly thicker at one end and tapering gradually. 



Growing as a parasite on an undetermined, hyphopodiate mycelium 

 on Anacardium (cashew). 



British Guiana: Rockstone, July 13, 1922, 253; Tumtumari, July 8, 

 1922, 65. 



This fungus in general characters is close to Perisporina from which it 

 differs in spore color, septation and in mycelium. If regarded as being 



" Theissen and Sydow 1. c. 



" Amaud, G. Les Asterinees. Ann. de TEcole nat, d'Agric. de. Montpellier. N. S. T., 

 16:1918. 



