172 Principles of Plant Culture. 



within full view, the fungi are in many cases discernible 

 only with the microscope, and reveal their presence only 

 by the death or injury of their host. The fungous para- 

 sites are very numerous and exhibit great diversity of 

 structure and habit. Some of them live only upon 

 enfeebled plants, while others attack healthy ones. Some, 

 as the pea mildew, grow upon the surface of their host, 

 drawing their nourishment through the epidermis; others, 

 like the peach curl and oat smut, grow within the tissues 

 of the plant upon which they feed. All of the latter 

 class send their fruiting parts to the surface of the host 

 plants to disseminate their spores in the open air. 



The fungi multiply from extremely minute spores (53) 

 that are produced in immense numbers, and when mature, 

 are very readily blown about by wind. Many of them 

 also multiply from thread-like organs called hyphce 

 (hy'-phse), something in the same manner as Canada 

 thistles multiply from their roots. 



322. Methods of Controlling Fungi are of three classes : 

 a Eemoving and destroying the affected parts; 



b Preventing the germination of the spores; 

 c Destroying the fungus itself by applying some 

 destructive material (a fungicide (fun'-gi-cide.)). 



323. Destruction of the Affected Parts is the most 

 effectual preventive known in cases where the fungous 

 disease attacks a portion of the plant whence it spreads 

 to the remaining parts, as in the black knot of the plum,* 

 the blight of the pear, apple and quince, f the red rust of 

 the raspberry and blackberry,]; and the corn smut. 



* Plowrightia morbosa. f Microccocus amylovorus. 

 J Cfeoma luminatum. \ Ustilago Maydis. 



