266 METHODS IN PLANT HISTOLOGY 



BASIDIOMYCETES 



This is an immense group, of which the smuts, rusts, mushrooms, 

 toadstools, puffballs, and bracket fungi are the most widely known 

 representatives. 



The smuts (Ustilagineae). — The smuts are abundant on wheat, oats, 

 corn, and various other plants. 



The smuts may be studied in the living material. The following 

 method, described by Ellis, is worth remembering: A supply of 

 smutted barley may be obtained by sowing soaked, skinned barley that 

 has been plentifully covered by Ustilago spores. In such material it is 

 easy to trace stages in the development of spores. Freehand sections 

 of ears about 12 mm. long show the mycelium and spore clusters. If 

 smutted ears be removed and kept floating on the water, the spores 

 continue to develop and often germinate. For paraffin sections de- 

 sirable stages should be fixed in Flemming's fluid or picro-acetic acid. 

 Delafleld's haematoxylin, foflowed 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 material is ingenious and is 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 solution (from 15 minutes 

 to 1 hour was sufficient for the fungus spores). Cover a slide with al- 

 bumen fixative, 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 (Uredineae). — Puccinia graminis, the common rust of 

 wheat and oats, is familiar to everyone. The urediniospores, or sum- 

 mer spores, known as the red rust, and the winter spores, known as the 

 black rust, are found in unfortunate abundance, but the aecium stage 

 on the barberry is not necessary for the vigorous development of rust 

 in the United States, and it is not nearly so prevalent as the red- and 



