PLANTS WUICIJ CAUHli DKJVA Y 



407 



shown in Fig. 'I'M). The long, branchiug appendages 

 of the rounded black bodies are very characteristie. 

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

 until some of the black bodies are ci'uslied; we may 

 then see the spore- sacs, containing four or more 

 spores . 



Mildews ai'e very common on both wild and culti- 

 vated plants 

 and do a large 

 amount of dam- 

 age. They do ^^^ ^'J'^' 

 not penetrate to 

 any great extent 

 into the leaf but 



a D S O r D nUtri- 230. Peritliecium of the common llildew of the Lilac ; spore- 

 Tnfinf Viv mp'ino sacs (asci) issuing from an opening producei 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:^ 



(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"; Loderaan: "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 189G by de 

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



