182 



Principles of Plant Culture. 



lime, sown with the seed, has proved beneficial by pre- 

 venting infection of the young plant. 



327. Fungi the Spores of which Survive the Winter 

 Within their Dead-Host Plants, as in the club-root of 

 the cabbage* and turnip, and the onion mildew,f may 

 be held in check to some extent by burning the fungus- 

 killed plants at the close of the season. 



328. Fungi that Infect their Host from Spores 

 Deposited On the Aerial Parts of the plant, as the 

 scab of the applet and pear, and the downy grape-vine 

 mildew may be held in check by applying a fungicide 

 (321) to the host plant, to destroy the spores as they 



FIG. 78. A scab spot mag- 

 nified. (After Trelease.) 



FIG. 77. Apple affected with 

 scab (the dark spots), Fusicla- 

 dium dendriticum. (After Scrib- 

 ner.) 



FIG. 79. Section through a 

 scab spot, highly magnified. 

 The egg-shaped parts at the 

 right are the spores. (After 

 Trelease.) 



alight upon it. Various compounds of copper and of 

 sulfur are destructive to the spores of fungi, and when 

 properly applied, are harmless to the plant. The cop- 



* Plasmidiophora Ttrassicae. 

 | Fusiclailiuin (ie/idri/icuni. 



t Peronoxpora Schleideniana. 

 \ Peronospora viticola. 



