Algas, Fungi, and Lichens. 



281 



bushes where these abound, producing 

 chains of spores, termed aecidiospores, in 

 cup-shaped cases (Fig. 144, B). These 

 spores become discharged, and when blown 

 to the surface of a leaf of wheat they grow 

 into it, and finally summer spores appear at 

 the surface of the leaf, as already described. 



It appears, then, that the rust of wheat 

 produces three kinds of spores and requires 

 two kinds of plants to run the full course of 

 its existence. The winter spores, however, 

 can establish themselves in the leaves of 

 wheat without the intervention of the bar- 

 berry, and the summer spores can also sur- 

 vive the winter and reproduce the fungus 

 on wheat the following spring. 



Other parasitic Fungi of common occur- 

 rence which often do great damage to the 

 plants of the field and garden are the 

 smuts and mildews. 



Fig. 143. 



Germinating te- 

 leutospore of 

 wheat rust. After 



TULASNE. 



Fig. 144. 



A, leai of barberry bearing aecidiospores of wheat rust. 

 B, cross section tlirough the barberry leaf, showing 

 groups of spores immersed in the tissue of the leat {B 

 after De Bary.) 



174. Toad- 

 stools. — The 

 toadstools are 

 too commonly 

 observed to re- 

 quire descrip- 

 tion here, and 

 only a brief ac- 

 count of their 

 structure and 

 ways of life will 

 be necessary. 

 The stem and 



