1921] MILES—LEAF SPOTS OF ELM 185 
which persists for a long time, finally cracking and breaking 
irregularly to allow the dispersal of the spores. They average 
800 win diameter. The hymenial layer is pseudoparenchymatous, 
composed of practically colorless cells which are almost isodia- 
- metrical in shape. This layer may be even thicker than that 
described for Gloeosporium ulmeum, although it presents an entirely 
different appearance, and on account of the absence of color does 
not at all suggest a stromatic base. The layer appears even 
thicker than it really is on account of the absence of all color from 
the epidermal cells, which have become entirely filled with small 
colorless crystals. This is true to a less extent of the adjacent 
layers of palisade tissue. The conidiophores are closely packed 
together, and are quite similar to those of Cloeosporium ulmeum 
except for their larger measurements, being 10-15 2-3 wu. They 
are not as darkly colored as are those of the preceding species, 
although they are not entirely hyaline. The apex is rather blunt, 
and the conidiophore terminates rather abruptly in a sterigma- 
like projection on which the spore is borne. Occasionally two of 
these sterigma-like processes occur on a single conidiophore. The 
conidia are much larger, especially in width, and vary considerably 
in form, from oblong-cylindric to ovate, elliptical, and even pyri- 
form. They measure 8-10X3~-3.5 mu (fig. 17), are one-celled, 
rounded at both ends, straight, and hyaline. In no case was the 
perithecium of Gnomonia or any similar fungus found associated 
with this spot. I consider it entirely distinct from the conidial 
stage of Gnomonia ulmea, and propose for the fungus the following 
name and description. 
Gloeosporium ulmicolum, sp. nov.—Spots epiphyllous, raised, 
gray on account of the black acervuli thickly scattered over the 
whitened epidermal cells, elongated, following the leaf veins, often 
extending the entire length of the secondary veins which have 
become browned far beyond the limits of the spot; acervuli 
epiphyllous, gregarious, subcutaneous, covered by the persistent 
darkened cuticle which finally ruptures irregularly to allow the 
dispersal of the spores, averaging 800 w in diameter, irregular in 
outline but usually elongated suborbicular; conidiophores in a 
closely packed layer, dilute-brown, cylindrical, usually nonseptate 
