PLANTS WHICH CAUSE DECAY 407 



shown in Fig. 230. The long, branching appendages 

 of the rounded black bodies are very characteristic. 

 Press on the cover-glass with a rubber pencil -eraser 

 until some of the black bodies are crushed; we may 

 then see the spore- sacs, containing four or more 

 spores. 



Mildews are very common on both wild and culti- 

 vated plants 

 and do a large 

 amount of dam- 

 age. They do 

 not penetrate to 

 any great extent 

 into the leaf but 



absorb nUtri- 930. Penthecmm of the common Mildew of the Lilac; spore- 

 TTIPnt bv mParm sacs (asci) issuing from an opening produce! by crushing. 



of short sucking organs which penetrate into the 

 epidermal cells. 



Most of the loss from plant diseases is preventable 

 by simple measures; among these are the following i^ 



(1) Spraying with chemicals (Bordeaux mixture, 

 sulphur, etc.) which do not injure the plant. 



(2) Destruction of diseased plants or portions of 

 them by burning; this of course destroys the spores. 



1 Consult Ward: "Disease in Plants"; Lodeman: "The Spraying of 

 Plants"; Ward: "Timber and Some of its Diseases"; Massee: "Text-book of 

 Plant Diseases"; also articles in the Year-Book of the U. S. Department of 

 Agriculture for 1895 by Waite and by Galloway and Woods; for 1896 by de 

 Schweinitz and by Howard; for 1899 by Galloway; for 1900 by von Schrenk. 



