22 Nelson The Genus Psilostrophe. 



throughout; crown leaves and lower stem leaves wanting at the time of 

 flowering. 



Type of the variety, as cited above, in the National Herbarium (No. 

 26,577). 



4. Psilostrophe tagetina (Nutt.) Greene. 



RiddeUia tagetina Nutt. Trans. Am. Phil. Soc., 7:361. 1841. Gray, 

 Syn. Fl., 317, probably in part only. 



Psilostrophe tagetina (Nutt.) Greene Pitt., 2:176. 1891. 



Even after segregating the species indicated as new in this paper the 

 specimens at hand show considerable variation and may still be an 

 aggregate, but to the writer the difference seems to be vegetative and 

 not congenital. Judging by the specimens the center of distribution is 

 New Mexico. 



Specimens examined. New Mexico: E. O. Wooton, 1894; id, No. 6, 

 1897; F. 8. and E. S. Earle, No. 374, 1900; A. A. and E. G. Heller, No. 

 3739, 1897; J. G. Smith, No. 25, 1897; G. R. Vasey, 1881; A. Fendler, 

 No. 461, 1847; J. T. Rothrock, No. 463, 1874. Arizona: Walter Hough, 

 No. 115, 1896; Comanche Plains, J. M. Bigelow, 1853. 



Somewhat aberrant and mostly distributed as Riddellia arachnoidea, 

 are the following from Texas: L. H. Dewey, 1891; G. W. Letterman, 

 No. 25, 1882; Newberry, 1859; Mex. Bound. Surv., No. 628. 



Still more aberrant and probably worthy of a varietal name are some 

 other Texan specimens which may be called: 



4a. Psilostrophe tagetina lanata, n. var.* 



Larger than the species, simple-stemmed or divaricately branched, 

 long-lanate, floccose-woolly at the crown; leaves simple or pinnatifid and 

 some of the stem leaves (often nearly all of them) sometimes deeply pin- 

 nately lobed; the lobes oblong-linear, entire or toothed; rays usually 

 larger than in the species. 



Specimens examined. Texas: G. R. Vasey, 1881 (type); Mex. Bound. 

 Surrey, No. 629 (paratype); W. L. Bray, No. 416, 1899; (?) J. Reverchon, 

 1879. Type and paratype in National Herbarium. 



5. Psilostrophe pumila (Jones) n. comb. 



RiddelKa tagetina pumila, Jones, Proc. Cal. Acad. Sci., (2) 5:700, 1895. 

 Psilostrophe Bakeri Greene, PI. Baker. 3:29. 1901. 

 This perfectly valid species is certainly the handsomest one in the 

 genus. That Mr. Jones' variety is the same as Dr. Greene's species 



*The type and paratype of Psilostrope tagetina lanata A. Nelson are in 

 the National Herbarium under the herbarium numbers, respectively, of 

 156,585 and 26,581. 



