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 

 aiiy'great extent 

 into the leaf but 



nutri- 2 30. Perithecium of the common Mildew of the Lilac; spore- 

 issuing from an P enin g Produce! by crushing. 



v means 



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 



(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"; Lodeinan: "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. 



