DISEASES OF WILD PLANTS. 91 



formed on the upper surface of the leaf of the Boerhavia (Boerhavia 

 spp.). This disease is very widely distributed, but apparently causes 

 little injury. 



Specimens collected: San Antonio, 1371, 3175; New Braunfels, 1697; Bas- 

 trop, 2033; Lockhart, 2075; CotuUa, 2135; Seguin, 2318; Victoria, 2527; Nur- 

 sery, 2574; Cuero, 25i)0; Stockdale, 2G0S; Gonzales, 2GSG; Kennedy, 2832. 



BROOMWEED. 



Rust {Aecidium chrysopsidis Ell. and Anders.). — On the stems 

 and leaves (much more abundantly on the stems) of the broomweed 

 {Gutierrezia texana (DC.) Torr. and Gray) are whitish or yellowish 

 pustules, the cluster cups. They form in such numbers on the main 

 stems and branches that these parts become brown and are killed. 



This rust has been described (13) as occurring on Gutierrezia eu- 

 thamia Torr. and Gray and is probably the same as the one on this 

 species, although no note of the fact has been found. 



Specimens collected: Victoria, 2538; Gonzales, 2679. 



BULL NETTLE. 



leaf -spot {Septoria jatropliae Heald and Wolf, 32). — This causes 

 the formation of very characteristic, brown, circular areas on the 

 leaves of the bull nettle {Jatropha stimulosa Michx.). These spots 

 vary in size from 1 to 5 mm. and are frequently somewhat irregular 

 in outline. At first they are dark brown with a darker, almost black, 

 border. Later the centers become tan and sometimes gray, but 

 always with a definite dark margin. The pycnidia are 120 to 150 /i, 

 brown and immersed wholly in the leaf tissues. The spores are rod 

 shaped or slightly clavate, hyaline, 40 to 50 by 3 /x and few septate. 



The spots frequently are so abundant that they fuse, causing the 

 drying of large portions of the leaf. 



Specimen collected: Austin, 2429 (type specimen). 



CAROLINA CL0\rER. 



Rust {Vromyces elegmis B. and C). — The minute brown sori 

 appear abundantly on the lower surface of the leaflets of Carolina 

 clover {Trifolium caroUnianum Michx.). 



Specimen collected : Austin, 3060. 



COCKLEBUR. 



Leaf-spot ( Cercospora xanthicola Heald and Wolf, 32. ) — This fungus 

 produces upon the leaves of the cocklebur {Xanthium spp.) numerous 

 circular or subcircular spots, 0.5 to 2 mm. (1 mm. average size) in 

 diameter, with dirty-gray or brownish centers surrounded by a nar- 



226 



