1921] MILES—LEAF SPOTS OF ELM 183 
and finally breaks away entirely, subrotund or irregular, averaging 
500 w in diameter, but often as large as 800 yu, epiphyllous, very 
rarely hypophyllous; conidiophores cylindrical, crowded, occasion- 
. ally with a septum near the base, 8-12 X1.5~2 u, terminating in a 
threadlike projection on which the spores are borne; conidia 
elongate-oblong or cylindric, bacillar, pointed at one or both ends, 
straight or very slightly curved, hyaline, one-celled, 5-6 X1-1.5 
in a dry condition or 8-10 X2-2.5 uw when freshly collected, and 
extruded in small white masses. 
Habitat on the living leaves of Ulmus americana, U. fulva, U. alata, 
U. racemosa, and U. crassifolia. Common. Conidial stage of Gnomonia 
ulmea (Schw.) Thiim. and constantly associated with it, the two stages occurring 
concurrently on the same leaf and spot. Type specimen on U. americana, 
collected at Urbana, Illinois, August 1919, and deposited in the herbarium 
of the University of Illinois. Differs from Gloeosporium inconspicuum Cav. 
in the very different appearance of the spots and in the larger size of its spores, 
and from Gloeosporium inconspicuum Cav. var. campestris Dor. in the charac- 
ter of the spots. 
INOCULATIONS WITH CONIDIA 
On April 25 a number of leaves of the American elm were 
placed in a moist chamber lined with filter paper, and at a definite 
point on each was placed a drop of distilled water containing a 
considerable number of spores of Gloeos portum ulmeum, the conidial 
stage of Gnomonia ulmea. On June 2 most of these spots were 
lighter in color than the remainder of the leaf, and on June 5 a 
few of them showed distinct conidial pustules entirely character- 
istic of the fungus with which the leaf had been inoculated. On 
the same day on which this experiment was started a number of 
leaves of a seedling elm, quite healthy in appearance and growing 
naturally in the open, were sprayed with a suspension of the same 
spores in distilled water by means of an atomizer, and the entire 
twig was inserted into an Ehrlenmeyer flask. The mouth of the 
flask was closed by means of a split cork in which a channel had 
been hollowed to fit about the twig. The flask was supported by 
means of props in such a manner that the twig remained in its 
proper position. On June 5 the entire new growth of the twig 
was found to be covered with a practically continuous layer of 
pustules of Gloeosporium ulmeum, all of which were extruding 
