116 STUDY OF COMMON PLANTS. 



Some of them, as the black mould, are saprophytic, — that is, 

 living upon dead organic substances; while others, like the 

 rust of wheat, are parasitic, — that is, preying upon living 

 plants or animals. They include moulds and other sorts 

 that function as scavengers, many destructive parasites that 

 yearly induce enormous losses of grain and fruits, and 

 also such conspicuous forms as the mushrooms, toadstools, 

 and puffballs, with many others that have no popular 

 name and are known only to special students. 



The vegetative part of a fungus consists of the mycelium, 



composed of hyphse, which may be distinct, or loosely felted, 



or in some of the more highly developed forms 



yoe ram. closely compacted into a fleshy or more or less 

 indurated mass. In many parasitic forms the mycelium 

 sends suckers into the cells, and by their means absorbs 

 the nutritive materials upon which the fungus feeds. 



Upon the mycelium is formed, sooner or later, the fruit- 

 bearing part of the fungus, — the carpophore. This may 

 have the simple form of a sporangiophore, such 



arpop ore. ^^ ^^ have Seen in the black mould, or a more 

 complicated structure, as, for example, the secidium fruit 

 of the barberry, or it may be still larger and more con- 

 spicuous, as in the case of mushrooms and their allies, in 

 which it shows a correspondingly higher differentiation. 



The carpophore bears the spores, which in the fungi 



exhibit a variety of form and structure not found in any 



other group of plants. In our study of the black 



''°"°' mould, and the rust of wheat, we have become 



acquainted with some of the simpler forms. There is 

 often a strongly marked distinction between the sexual 

 and non-sexual spores. Thus the sporangiospores of the 

 black moulds are very much smaller, and their protective 

 covering less strongly developed than that of the zygo- 



