Gnomonici cry thro stoma , Pers. 587 
he describes the external features of the disease with extreme brevity. After 
considerable trouble, however, I was able to find Cherry leaves which con¬ 
tained the parasite in the very young stages of development. The first 
signs of disease are the presence of faint yellowish patches either on the 
margin or near the midrib of the leaves, though when these patches are seen 
for the first time they hardly suggest disease of a serious nature. 
On cutting hand sections through leaves affected in this way the 
characteristic mycelium of Gnomonia erythrostoma could be discerned. 
These yellowish patches are first recognizable in the early part of July. 
They increase in size and become more clearly yellow in colour. Towards 
the end of August spermogonia become visible. They are formed in enor¬ 
mous numbers, and appear externally as tiny circular spots on the under 
surface of the yellowing parts of the leaves and just visible to the naked eye. 
With the production of spermogonia the diseased portion of the leaf becomes 
brown. 
Methods. 
Portions of diseased cherry leaves were fixed in various fluids. Flem¬ 
ming’s weaker and stronger solutions, Gilson’s fluid, Juel’s fluid, and acetic 
alcohol were tried, but as the first-named solution proved to be by far the 
most satisfactory fixative it was generally used. An air-pump to aid fixation 
was employed when necessary. The material was cleared in chloroform or 
in cedar oil and embedded in paraffin of about 52 0 C. melting point. Micro¬ 
tome sections were cut from 5 ju-15 [jl in thickness and were stained either in 
gentian violet and orange G, or in Heidenhain’s iron-alum-haematoxylin, 
with a counter-stain of orange G, Congo red, or erythrosin. 
Vegetative Mycelium. 
Frank (17) states that the ascospore on germinating upon the surface 
of the leaf gives rise to an appressorium, a structure which doubtless per¬ 
forms mainly an anchoring function. The appressorium puts out a short 
tube which penetrates the cuticle directly, thus entering an epidermal cell. 
The parasite enters the intercellular spaces of the mesophyll by means 
of another short hypha which penetrates the inner wall of the epidermal cell. 
Evidence of the production of appressoria and of the penetration of epidermal 
cells was also seen in my preparations of the young mycelium. 
The subsequent development of the mycelium is intercellular. A general 
view of it is seen in Plate XLVIII, Fig. 1. The mycelium consists of broad 
hyphae which are septate and branch at intervals ; it ramifies most abundantly 
in the spongy parenchyma, but not infrequently branches are put out which 
force their way between the closely packed palisade cells. Narrowings 
