THE FUNGI 257 
Examine first with m.p., and then with h.p. Note: 
(a) The forms of the cluster-cups at various stages of growth. 
Compare with the cup on an anemone leaf, shown in Fig. 181. 
(6) The structure of the cup, surrounded by a layer of mycelium, 
next to which comes the peridium, or wall of the cup. The latter is filled 
with chains of spores (ecidiospores). Draw the cup with its contents. 
(c) The size and shape of the mature t 
spores which separate from the ends of 
the chains. 
(d) The cavities, smaller than the 
cluster cups and on the opposite surface 
of the leaf. These produce great num- 
bers of minute cells which now appar- 
ently are of no service in the life of the 
fungus, though they may once have been. 
831. Red-Rust Stage and Black-Rust 
Stage, Gross Structure. — Examine with 
the magnifying glass the surface of the 
leaf sheaths and stems of wheat or other 
grain or of quick grass (A gropyrum re- 
pens) collected in early summer and other 
specimens collected in autumn. Note 
the rust streaks extending lengthwise 
of the leaf sheaths and the stems. De- 
scribe the precise color of these streaks 
in the early- and the late-collected ma- 
terial. Draw some of the best defined 
streaks of each kind. In preserved mate- 
tial the early rust may have lost a good 
deal of its color. 
332. Red Rust, Minute Structure. — 
Pick out with a scalpel or a knife point some spores (uredospores) from 
a streak of red rust. Tease the material out with dissecting needles 
in a drop of water on a slide. Cover and examine with h.p. Note: 
(a) The shape of the spores and the attachment of each to a 
stalk (Fig. 182). 
1 If the spores are dry, shrunken, and opaque they may first be soaked for 
a few minutes in a five-per-cent solution of potassium hydrate. 
‘Fie. 182. A Group of Spores 
of Wheat Rust (Puccinia 
graminis). (x about 440.5 
U, U, Uredospores; ft, a 
teleutospore. 
