14 MICROBES, FERMENTS, AND MOULDS. 



microbes, properly so called, are still often assigned to 

 the class of fungi. We shall speak of them separately, 

 and give our reasons for distinguishing them from 

 true fungi. 



Hymenomycetes are the fungi which possess the 

 hymenium or umbrella; all the edible species are 

 included in this class, together with a great number 

 of extremely pokonous species. They are generally 

 of considerable size, and only a few among them are 

 true parasites ; they do not, therefore, enter into the 

 plan of this work, and, in spite of the interest they 

 present, we shall content ourselves with the brief 

 notice of them we have just given. The other groups 

 must, however, detain us longer. 



II. THE BASIDIOMYCETES : UREDTNE^, THE RUST OF 

 WHEAT AND Gn ASSES. 



The name of cereal rust is given to a parasitic 

 affection caused by a minute microscopic fungus which 

 is developed on the leaves of wild and cultivated 

 grasses. This rust appears in the form of orange 

 patches, which gradually spread over the blades of 

 wheat and other grasses, and its common name is 

 due to this colour. Many of the plants belonging 

 to other families are attacked by analogous parasites, 

 and these fungi are all assigned by naturalists to 

 the genus Uredo, and to the family of the Basidio- 

 mycetes or Uredinece. 



