380 PEACTICAL BOTANY 



round. In the chapters on fungi there were given detailed 

 accounts of the processes and structures that have to do with 

 the nutrition of several kinds of saprophytic as well as para- 

 sitic fungi. 



346. Other parasitic fungi. Usually parasitic fungi are ex- 

 tremely dependent, since most of them can live on but one or 

 at most a few kinds of hosts. If for any reason these hosts are 

 lacking, or if the parasite is not properly placed upon or within 

 the host, the parasite fails. Wheat and oat rust may thrive 

 upon wheat and oats and produce their summer and winter 

 spores in great quantities (Sect. 232). But in entire absence 

 of wheat and oats the parasite would probably soon disappear. 

 It is apparently well adjusted to life upon these hosts, but, 

 correspondingly, thoroughly dependent upon them for nour- 

 ishment. Such is the case with many parasitic fungi. Their 

 close adjustment to life upon one type of host is accompanied 

 by complete dependence upon that host. It may be easier for 

 the dependent plant to secure food when it is well located, but 

 it encounters serious dangers when not well located. 



347. Degrees of dependence among flowering plants. Some 

 dependent flowering plants, like the woodbine or Virginia 

 creeper, are almost independent. A woodbine may grow in the 

 open and attain its full size ; but in dense woodlands woodbines, 

 grapevines, and many other climbers can only make a normal 

 growth by raising themselves into the light by climbing up 

 the trunks of trees. Similar degrees of dependence are found 

 among the members of most of the other groups of plants 

 described in the succeeding sections of this chapter. 



348. Kinds of dependent flowering plants. The principal 

 groups into which dependent flowering plants are divided 

 are as follows: 



(1) Lianas, or climbers. 



(2) Epiphytes, or plants which live perched upon other 

 plants. 



(3) Saprophytes, or plants which live on the products of 

 the decay of organic matter. 



