48 



Diseases of Economic Plants 



readily be distinguished, however, by two characters: first, 

 the manner in which the leaves droop and mat together, 



which is quite different 

 from the habit of the 

 blight, the leaves of 

 which neither droop nor 

 become matted; second, 

 Ijy the presence of small 

 sclerotia, white when 

 young, cinnamon-brown 

 when mature, upon the 

 twigs adjacent to the 

 affected leaves. These 

 sclerotia usually meas- 

 ure about 2-3 mm. 

 in diameter. Together 

 with the sclerotia and 



J'slk ' \ d ^ '^'' extending along the 



il^l^^HftpJmv •• ^'^^^ longitudinally are 



^mx Imm^mJm^S ' q^^q found silvery, glis- 



tening, thread-like, fun- 

 gous growths. 



This fungus hiber- 

 nates in the sclerotia 

 on or near the terminal 

 Inid and thence invades 

 the new twigs as they 

 develop, reaching out 

 upon each leaf, spread- 

 ing over its under sur- 

 face in almost invisible 

 thinness, and causing it 

 to droop, die, and eventually to fall away. Thus, in early 

 autumn, such trees are nearly or quite defoliated. The 

 fruit may also be invaded by the fungus. 



Hypochnose, first described from Brazil, is known from 

 Maine to Florida and Texas. It seems to be especially de- 



FlG. 



22. — Hypochnose, showing mat- 

 ting of leaves. Original. 



