Seaver: North American Hypocreales 21 



by the thin, whitish epidermis of the host, scattered over whitish 

 patches on the substratum; ostiolum forming a disc-like expan- 

 sion above the surface of the epidermis, with a distinct perfora- 

 tion in the center, slightly hairy, especially near the margin of 

 the disc, where the hairs appear as a delicate fringe; perithecia 

 200 mic. in diameter ; asci clavate, 8-spored, 30-45 X 5 mic. ; 

 spores mostly 2-seriate above, often i-seriate below, fusoid, with 

 usually 2 large oil-drops, and 1-2 smaller ones toward either 

 end, 10 X 2-2.5 mic -> paraphyses present, delicate. 



On herbaceous stems (Ambrosia trifidaf). 



Type locality: Fargo, N. Dakota. 



Distribution : Known only from type locality. 



The perithecia of the present species are so minute that they 

 are easily overlooked and were first noted in connection with 

 the study of other species of fungi. They are scattered over 

 whitish patches on the surface of the substratum and although 

 the substratum is whitened where the perithecia occur there is 

 apparently no superficial mycelial growth. Two collections of 

 the species were made by the writer in the same locality near 

 Fargo. 



The genus Charonectria Sacc. differs from the present genus 

 in possessing septate instead of simple spores. The presence or 

 absence of the septum in case of very small spores is sometimes 

 difficult to determine and in the North Dakota specimen the 

 spores which have two large oil-drops often appear to be septate 

 but no definite septum could be made out. The genus Charonec- 

 tria is also represented in North America by a single species 

 which is quite different from the species here described, not only 

 in the presence of septate spores but in the size of both plants 

 and spores as well. 



Nectria semenicola sp. nov. 



Conidial phase consisting of a white mycelial growth which 

 covers the substratum, finally heaping up at various points 

 forming pinkish stomata ; conidiophores erect, much branched, 

 branches ascending perpendicularly, bearing at their summits, 

 elliptical, hyaline conidia ; conidia 5-7X2-3 mic, with 1-2 

 oil-drops. 



Perithecia cespitose in small, dense clusters, with numerous 

 scattered individuals; clusters confluent, often covering the most 



