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. 



(b) 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 (cecidiospores). Draw the cup with its contents. 



(c) The size and shape of the mature ^ 

 spores which separate from the ends of 

 the chains. 



(rf) 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. 



331. 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 {Agropyrum 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- 

 rial 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. 



Fig. 182. A Grou|) of Spores 

 of Wheat Rust (Puccinia 

 graminis). (x about 440.) 



u, u, uredospores ; t, a 

 teleutospore. 



