Fungi 



203 



water, the spores continue to develop and often germinate. For 

 paraffin sections desirable stages should be fixed in Flemming's fluid 

 or picro-acetic acid. Delafield's haematoxylin, followed by a very 

 light touch of erythrosin or acid fuchsin, will give a good stain. 



For a study of the germinating spores and conidia, cultures may 

 be made in beerwort on the slide or in watch crystals. Harper's 

 method of making preparations from such ma- 

 terial is ingenious and will undoubtedly prove 

 valuable in making mounts of various small plant 

 and animal forms. A drop of the material is 

 taken up with a capillary tube and is then gently 

 blown out into a drop of Flemming's weaker solu- 

 tion (15 minutes to 1 hour was sufficient for the 

 fungus spores). Cover a slide with albumen fix- 

 ative, as if for sections. A drop of the material, 

 without previous washing, is drawn up into the 

 capillary tube and touched lightly and quickly 

 to the surface of the albumen. A series of such 

 drops, almost as small as the stippled dots in a 

 drawing, may be applied to the slide. The fixing 

 agent may now be allowed to evaporate some- 

 what, but the preparation must not be allowed 

 to dry. As the slide is passed rapidly through 

 the alcohols, the albumen is coagulated, and the 

 preparation may be treated just as if one were 

 dealing with ribbons of sections. 



The Rusts (Ureclineae). -Puccinia graminis, 



the common rust of wheat and oats is familiar to everyone (Figs. 

 56, 57). The uredospores, or summer spores, known as the red rust, 

 and the winter spores, known as the black rust, are found in unfortu- 

 nate abundance, but the aecidium stage on the barberry is not neces- 

 sary for the vigorous development of rust in the United States, 

 and is seldom found. Most teachers are obliged to depend upon 

 botanical supply companies for this material. There are, however, 

 various aecidia which are as good, or even better, for morphological 

 study. The aecidia growing on Euphorbia maculata (spotted spurge) 



FIG. 57. Puccinia 

 graminis: A, uredo- 

 spores on oats; B, 

 germinating teleuto- 

 spore. X375. 



