THE FUNGI WHICH CAUSE PLANT DISEASE 243 



G. theae Bern. "* grows on tea leaves. 



G. (Laestadia) buxi Desm. The perithecia develop on box 

 leaves. It is probably saprophytic although sometimes considered 

 a parasite. 



Stigmatea Fries (p. 236) 



Perithecia subepidermal, or subcuticular, thin, black; asci 

 oblong, subsessile, 8-spored; spores ovoid-ellipsoid, 2-celled, yel- 

 lowish or hyaline; paraphyses present. The 

 ascigerous stage of two species of Entomo- 

 sporium are said by Lindau*' to belong to 

 this genus. Atkinson, however, places them in 

 the genus Fabrea, see p. 149. 



S. juniperi (Desm.) Wint., on living leaves 

 of Juniperus in Europe and America and on _ ,,, „ . 



CT ..-,,.. . Fio. 17b.— Stigmatea. 



beqUOia m Callforma. Asci and spores. 



Perithecia scattered, lenticular or subhemi- -A^^ter Winter. 

 spheric, rough, 200-300 fi in diameter, asci rounded and obtuse 

 above, abruptly tapering below into a short stipe, 60-70 x 20 /i; 

 spores ovate-lanceolate, unequally 2-celled, yellowish-hyaline, 16- 

 25 X 6-8 II. 



S. alni occurs on alder leaves in Europe. 



Mycosphserella Johans. (p. 236) 



Perithecia subepidermal, suberumpent, globose-lenticular, thin, 

 membranous, ostiole depressed or short papillate; asci cylindric 

 to clavate, 8-spored; spores hyaUne or greenish, ellipsoid, 2-celled; 

 paraphyses none. 



This large genus of over five hundred species formerly known as 

 Sphaerella contains several serious plant pathogens. It is often 

 found in its conidial forms as: Ramularia, Ascochyta, Septoria, 

 Phleospora, Cercospora, Ovularia, Cylindrosporium, Phyllosticta, 

 Graphiothecium, Phoma, Diplodia or Septogloeum. In many cases 

 the relationship of the ascigerous and conidial forms is as yet but 

 imperfectly known. The perithecia are usually found late in the 

 season, often only on leaves that have borne the conidial stage in 

 the summer and have then wintered. 



