Plants as Affected by Fungous Parasites. 181 



ous 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 

 (52) 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 

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

 Canada thistles multiply from their roots. 

 « 322. Methods of Controlling Fimgi are of three 

 classes : 



a — Removing and destroying the affected parts; 



b — Preventing the germination of the spores ; 



c— Destroying the fungus itself by applying soiar 

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



323. Destruction of the Affected Farts 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,t the 

 red rust of the raspberry and blackberry, J and 1he 

 corn smut.§ 



* Plowrightia morbosa. 



t The organism causing blight Is a bacterium, Pacillus amyglovorus, 



t Gymnoconia PecMana. § VstUarjn Maydib. 



