188 



THE ASCOMYCETES 



sweet potatoes, have been connected with Fusarium. Isaria con- 

 stitutes the conidial stage of Cordvceps, Sphacelia that of Clavi- 

 ceps, Fusarium tliat of Neocosmospora, and \>rticillium that of 

 Hypoiiiyces ochraceus and H. chrysosper?mis. Diplocladhim 

 vibms is connected with Hypomyces later itms, and Trichothe- 

 chnn cand'idimi with H. roselhis. My co gone perniciosa and M. 

 rosea parasitize mushrooms and are chlamydosporic stages of 

 Hypomyces. Sepedoniimi chrysospervmvi is the chlamydosporic 



staore of Hypomyces chryso- 

 speiiims, \\'hich attacks Bole- 

 tus. Gibberella saiLbinettii (G. 

 zeae) appears late in the sea- 

 son on cereals whose heads 

 (inflorescences) are blighted 

 by the Fusarium stage. Ephelis 

 constitutes the conidial stage 

 of Epichloe, Dothichloe, and 

 Balansia. V erticilliiim globii- 

 Ug-erinJi is connected ^^'ith 

 Fodocrea ahitacea. 



Representative forms. In 

 the accounts that follow brief 

 mention will be made of a few 

 species regarded as representa- 

 tive of this rather large group. 

 In Nectria, containing over 250 species, are some very important 

 plant pathogens. Nectria galUgena causes a canker disease of 

 pomaceous trees in Europe and has been reported to attack pears 

 in the Pacific Northwest [Zeller and Owens (1921)]. Cayley 

 (1921) found ascogonial coils in developing perithecia but was of 

 the opinion that they do not function to produce ascogenous hy- 

 phae. She also observed pvcnidia, which may well have been 

 spermogonia. In the eastern United States N, ditiss'nna causes 

 "target-spot" cankers on basswood, red maple, birches, ^\'alnut, 

 and yellow poplar. In the Maritime Provinces of Canada N. coc- 

 cinea is associated with the scale insect, Cryptococciis jagh in the 

 destruction of beech [Ehrlich (1934)]. 



The Genus Thyronectria, monographed by Seeler (1940), con- 

 tains species having muriform ascospores. In some species these 



Fig. 70. Neocosmospora vasiniecta. 

 A. Surface view of perithecium, B. 

 Ascus contains thick-walled 'asco- 

 spores. 



