﻿iqi6] LONG-RAVEN ELI A 421 



5506, W. H. Long); also collected at Tucson, Arizona, on Acacia constricta 

 p wcispina (nos. 5507 and 5508, W. H. Long). 



On a recent trip to Tucson, the writer's attention was called by Professor 

 Thornber, of the University of Arizona, to a species of Ravenelia on Acacia 

 constricta paucispina which formed small witches' brooms. The host was 

 growing on the grounds of the University of Arizona immediately adjacent to 

 a tree of Acacia greggii which has heavily infected with R. vcrsatilis. The 

 close proximity of the two host trees and the fact that both bore witches' 

 brooms suggested the possibility of the Ravenelia on Acacia constricta paucis- 

 pina being R. versatilis. However, a microscopic examination of the rust 

 revealed marked differences in the urediniospores which easily separated it 

 from R. versatilis. On this trip, the writer revisited a locality at El Paso, 

 Texas, where he had collected a Ravenelia in August 191 5 on an unidentified 

 host. This host proved to be Acacia constricta paucispina, and the Ravenelia 

 on it was identical in every way with that collected on the same host at Tucson, 

 Arizona. The specimens of R. thornberiana collected at Tucson had only 

 fresh telia intermixed with old and weathered uredinia. The collection of this 

 rust made by the writer at El Paso in August 1915 consisted of fine uredinial 



was good telial material. For this reason, the material collected at El Paso 

 is made the type for the species. 



The number of species of Ravenelia previously described whose uredinia 

 or telia cause pronounced witches' brooms is limited to 4 species, namely, 

 R. versatilis on Acacia greggii. R. jragrans on Mimosa fragrans, both American 

 species; and two African species, R. volkensii P. Henn. on Acacia sp. (only the 

 teliospores of which are known), and R. natalensis Syd. and Evans on Acacia 

 hirtella (which has aecia as well as uredinia and telia). Of these 4 species, 

 R. vcrsatilis is the only one which has urediniospores with two rows of germ 

 pores, but this species has one row at the equator and the other near the base 

 of the spore, while R. thornberiana has its two rows of germ pores equidistant 

 from the equator. The lower halves of the urediniospores of R. versatilis are 

 hyaline, while the urediniospores of R. thornberiana have walls uniformly 

 colored. 



There are only two described species of Ravenelia with germ pores in two 

 rows equidistant from the equator, namely, R. siliquae Long on Vachellia 

 famesiana and R. acaciac-pennattdoe Dietel on Acacia pennatula. R. thorn- 

 beriana differs from R. siliquae in having very small uredinia and in the shape 

 and size of its urediniospores. It differs from R. acaciae-pennatulae in having 

 smooth teliospore heads. 



Ravenelia reticulatae, sp. no v. 



O. Pycnia unknown. 



II. Uredinia hypophyllous, scattered, punctiform to elliptical, 

 very small, 0.25-0.5 mm. across, subcuticular, tardily naked, 



