DISEASES OF WILD PLANTS. 103 



SUNrLOWER. 



Leaf-spot {Cercospora pachypus Ell. and Kellerm.). — Irregular, 

 angular spots, 1 to 5 mm. in diameter, becoming dark brown, are 

 formed on the foliage of the sunflower {Helianthus spp.). These 

 areas fuse and, accompanied by more or less chlorosis, the leaves are 

 killed. 



Specimen collected : Hondo, 1989. 



Powdery mildew {Erysiphe cichoracearum DC). — Upon the upper 

 side of the leaves appear conspicuous white patches, often covering 

 the greater part of the leaf surface. Only the conidial stage was 

 observed. 



Specimen collected : San Antonio, 3159. 



Rust {Puccinia helianthi S.). — The rust sori are formed in abun- 

 dance on both wild and cultivated forms, frequently so as to render 

 the under surface quite brown. 



Specimens collected: San Antonio, 1357, 1388, 1392, 1780, 3162; Seguin, 2300; 

 Cuero, 2576; Flatonia, 2718. 



TICK TREFOIL. 



Rust [Uromyces hedysari-paniculati (S.) Farl.). — The yellowish- 

 brown sori on tick trefoil {Meibomia sp.) are very numerous on the 

 lower surface of the leaves and sparse on the upper surface. 



Specimen collected : Austin, 343. 



TROMPILLO. 



Dodder {Cuscuta sp. ?). — This parasite on the trompillo (Solanum 

 elaeagnifoliuTTv Cav.) was not flowering, and consequently could not 

 be identified. 



Specimen collected : Bastrop, 2029. 



Nematode leaf -curl {Tylenchus sp.). — This is quite common, caus- 

 ing the leaves to be curled and much hypertrophied. (PI. XVIII, 

 fig. 3.) 



Specimens collected: Austin, 1262; Kennedy, 2833. 



VINCETOXICUM. 



Leaf -mold {Cercospora hellynckii (Westd.) Sacc). — An olivace- 

 ous, brown, diffuse coating is formed on the leaves of vincetoxicum 

 {Vincetoxicum spp.). The description (46) of the fungus states 

 that it occurs on the lower leaf surface, but our specimen shows 

 conidiophores on both surfaces. In other characters the agreement 

 is satisfactory. 



Specimen collected: Austin, 312. 

 226 



