1921} MILES—LEAF SPOTS OF ELM 181 
stroma, and which now have become the cells of the hymenial 
layer from which the conidiophores arise. It is also frequently 
found deposited between the cells of the epidermis immediately 
beneath the stroma. 
These epidermal cells are 83 changed to any considerable 
extent except for crystalline sub lly found deposited 
in them. The fungal hyphae grow down between them and 
crowd them apart somewhat, but they do not lose their arrange- 
ment as a definite layer. The hyphae of the fungus do not pene- 
trate the cells of the host. The conidiophores are crowded together 
into a very compact layer, and are 8-12 yw long by 1.5—2.5 py thick. 
They are without septa, except for an occasional one near the base, 
and terminate in a threadlike projection on which the spores are 
borne. The conidia are elongate-oblong or cylindric, bacillar, 
pointed at one or both ends, straight or sometimes slightly curved, 
one-celled, hyaline, and measure 5-6 X1-1.5 uw (fig. 15) in a dry 
state, but 8-10 X 2~2.5 » when freshly collected. 
Since there is no fungal covering to the conidial layer, the 
fungus falls into the family Melanconiaceae, and its other charac- 
ters indicate beyond a doubt that it is a member of the genus 
Gloeosporium. It seems to be quite characteristic of Gnomonia to 
have a conidial stage which is melanconiaceous in character. 
Gnomonia padicola has as an imperfect stage Asteroma Padi, but 
according to KLEBAHN (26) no true pycnidium is formed. Gloeo- 
Sporium nervisequum is connected with Gnomonia veneta, Mars- 
sonina Juglandis with G. leptostyla, Gloeosporium quercinum with 
G. quercina, Gloeosporium Caryae with G. Caryae, Gloeosporium 
Tiliae with G. Tiliae, and Leptothyrium alneum with Gnomoniella 
tubiformis. KLEBAHN (25) has shown also in connection with 
Leptothyrium alneum that no true pycnidial covering is formed, 
and that consequently it is melanconiaceous in structure. Sac- 
CARDO (30) also remarks concerning this species ‘‘(perithecio) 
subinde tamen spurio et ex epidermide mutata et atrata formato.” 
The genus Gnomonia contains a number of species which form 
no conidial stage, or at least whose conidial stage has not yet 
been discovered. In so far, however, as the conidial stages have 
been established in the genus, it is evident that they conform to a 
