ORNAMENTAL PLANTS 481 



the leaves. No pycnidia are present, but the centers of the 

 spots are darkened by the presence of hyphae. 



Phyllostictose (Phyllosticta Violas Desm.). — Straw-col- 

 ored or white, circular spots about 3 mm. in diameter, 

 similar to the last except for the presence of pycnidia, 

 are produced upon the leaves. 



Downy mildew (Peronospora Violce DeBy.). — The downy 

 mildew is in general character like that of the grape. The 

 spots are indefinite, and affected plants droop and die. 



Gloeosporiose, anthracnose {Glaeosporium Violce B. & Br.). 

 — The anthracnose often begins at the edge of the leaf, as 

 an irregular discoloration which extends inward, eventually 

 blighting the whole leaf. 



Thielaviose {Thielavia basicola (B. & Br.) Zopf.). — 

 Affected plants are stunted and yellow. The underground 

 parts show numerous dark spots of dead tissue which often 

 involve the roots for considerable distances. The disease 

 is the same as that of tobacco. 



Marsoniose, leaf spot {Marsonia Violce (Pass.) Sacc). — 

 This disease seems to be rare. The spots are smaller 

 than with other diseases, usually only 2-3 mm. in diameter, 

 and are reddish. When abundant, they cause yellowing 

 of the intervening tissue and result in serious injury to the 

 leaves. 



Rhizoctoniose. See p. 61. 



Zygodesmose (Zygodesmus albidus Ell. & Halst.). — This 

 mold forms a white, flour-like coat over the leaf. 



VIRGINIA CREEPER 



Phyllostictose (Phyllosticta ampelopsidis E. & M.).^: 

 The spots occurring upon the leaves and shoots are iden- 

 2i 



