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the plane of the epidermis, and containing frequent septa. The stroma 
mass is colorless at lirst and shaped like a double convex lens. The 
hyphse composing it are adherent along their whole course and may 
branch. The central portion is often composed of larger, more trans¬ 
parent hyphrn. When the cuticle is finally ruptured the shape of the 
stroma may change considerably, from the fact that it meets no further 
resistance to its upward growth. It is also from this time on that the 
changes which cause the fungus to be so variable take place. Some¬ 
times the free ends of the hyphse bear spores over the entire surface so 
that the stroma forms a compound sporophore, but usually the large 
cells comprising the center of the stroma mass break down, and the en¬ 
tire center becomes separated from the outer portions and may pass 
out through the opening in the cuticle. In this case spores are borne 
around the circumference of the stroma and the cavity left in the center 
develops basidia and spores on its sides, thus producing a pseudo- 
pcynidium. The amount of the stroma that disappears after the cuticle 
is ruptured varies exceedingly. In some cases the original mass seems 
to remain and grow dark colored. In other cases a large amount of 
stroma still remains, but it becomes dark colored, and enough of the 
original mass has disappeared so that the spores are borne on a very 
concave surface. The stroma grows dark colored as soon as the cuticle 
is ruptured, but the lower part of the central portion usually remaius 
colorless except in very old pustules. In some of these, especially on 
the apple, it looks as if the stroma had greatly increased in quantity 
and in a measure at least lost its spore-bearing property. Whether 
this apparent increase is due to a growth from the base of the stroma 
has not been directly observed, but from the appearance of the sections 
this conclusion is almost irresistible, and the fact that the base often 
remains colorless below the center supports such a view. Examples 
of this are frequent on the grape, but on the apple the older dark-colored 
pustules are especially large and after a time seem to stop forming- 
spores. When kept for a long time in a moist environment the ends of 
the hyphae sometimes grow out into long dark-colored filaments. 
Besides these more common forms there are cases where the stroma 
almost completely disappears after the cuticle is ruptured, and the re¬ 
sult is a typical Glcesosporium form, viz, rather long basidia borne on 
a thin stroma and bearing oblong spores at their free ends. Still 
another case was found where, instead of a true stroma, the hypliae 
were independent down to the very thin, irregular layer of pseudo par¬ 
enchyma always at the base of the parallel threads; thus forming extra¬ 
ordinarily long basidia with spores at their ends. 
Spores .—The spores are unicellular but may become two or even 
three celled at the time of germination. They are colorless singly but 
flesh colored in mass, irregularly oblong, sometimes curved and often 
pointed at one end, or even ovate. They vary greatly in size as well as 
in shape, and in the case illustrated in Fig. 4 are much longer than 
23(^3—Ko, 4-3 
