12 



TALKS AFIELD. 



genuine spores, or " resting spores," are in 

 the substance of the leaf itself. The rust of 

 wheat, the scab on apples, and many other 

 forms of plant diseases 

 are similar in nature to 

 the grape mildew. The 

 manner in which the 

 ^^^* ^^' spores of some fungi are 



borne is shown in Fig. 13, which represents 

 a magnified cross-section of the plum-knot, 

 so much dreaded by horticulturists. In the 

 peculiar club-shaped receptacles or asci are 

 seen the spores. 



The Polypores include those peculiar 

 shelf - like fungi 

 which grow on 

 losrs and decaA^ino; 

 trees. They may 

 be recognized b 

 a reference to 

 Fiff. 14. These 

 fungi are pecul- 

 iar in having a 

 hard and dura- 

 ble substance, al- 

 though a few of 

 them are soft in 

 texture. The genus Polyporus comprises 



my 



Fig. U. 



