246 BOTANICAL GAZETTE [october 



rounding wall is composed of several (five to eight) layers of myce- 

 lium. As the spore cavity becomes distended the wsll becomes 

 thinner, until at maturity it is composed of only one, two, or three 

 layers of mycelium, while the region of the ostiolum becomes one 

 layer thick and eventually ruptures. 



This fungus clearly belongs to the section Hyalodidymae Sacc. 

 of the SPHAERIOIDEAE Sacc, and seems closest in affinity to the 

 members of the genus Ascochyta. The possession of a slight beak, 

 which however is always very small and often entirely absent, might 

 throw it into the genus Rhyncophoma Karst., but members of that 

 genus are typically upon wood, usually saprophytic, and have a 

 more pronounced beak. 



Since no Ascochyta, or indeed any other species of the Sphaerioideae 

 Hyalodidymae, which could by any possibility be identical with the 

 species considered in this paper, has come to my notice as growing 

 upon the chrysanthemum or any of its kin, I regard this as a new 

 species, for which I give the following description. 



Ascochyta Chrysanthemi, n. sp. — Perithecia few, immersed, early 

 erumpent, single or scattered, round, hemispherical, amber colored, 

 100-200 /^, mostly about 150 z^; ostiolum central, small, dark bor- 

 dered, often raised by a short neck; surface reticulate, pycnidia on 

 agar media irregular, often with two ostioles and varying much in 

 size, black in color. Mycelium abundant, innate, also superficial, 

 aerial, floccose, richly septate. 



Spores oblong, straight or irregular, 3 to 6 . 2 X 10 to 20 /a, mostly 

 6.2X10/^5 ends obtuse or acute; septum usually one, often obscure, 

 rarely 2 or 3, usually without constriction until germination; proto- 

 plasm vacuolate, hyaline or light pink in mass. 



H.\bitat: in corollas, heads, petioles, and stems of cultivated plants of 

 Chrysanthemum indicum^ causing blight. North Carolina. 



CULTURE CHARACTERISTICS 



Thermal relation. — Cultures in Petri dishes on cow pea agar were 

 placed in darkness at three temperatures with the results appearing 

 in the adjoining table. 



