APRIL, 1919. XANTHIUM MILLSPAUGH AND SHERFF. 35 



of Mexico until shortly before Wallroth's publication of the name X. 

 saccharatum) . l 



Of X. affine Greene, X. californicum Greene 2 and X. acutum Greene, 

 we have seen the types (all in Hb. Greene); of X. affine we have seen 

 also various cotypes. So different do these forms appear at first that one 

 might well mistake them as typifying three distinct species. However, 

 the large number of herbarium specimens that we have examined from 

 the Pacific Coast show that specific segregation is entirely impossible. 

 So polymorphous does X. pennsylvanicum become in its western range 

 that, in California alone, as many as six or seven forms may be found. 

 In the eastern part of the United States, X. pennsylvanicum displays 

 much less variation, both in fruits and in general habit. 



13. Xanthium calvum sp. nov. PI. XII. 



Caulis erectus, rubescens, saepe maculis purpureis parvis longitu- 

 dinalibus punctatus, subscabridus aut infra etiam glaber, circ. 4-9 dm. 

 altus. Folia ovato-cordata aut ovato-triangulata, ad basim vel orbicu- 

 lata vel truncata vel cordata, plerumque atro-viridiora, crenato-dentata, 

 saepe dentato-lobata, setulis minutis adpressis scabrida, petiolis adjectis 

 0.6-2 dm. longis, petiolis laminis subaequantibus. Fructus (PI. VII, 

 f. 13; PI. IX, ff. 11-12) pauci aut numerosi, corpore crasso ovato- 

 fusiformi fusco, utrinque subacuto, exteriore facie breviter et minime 

 pubescenti, glanduloso, aculeis subremotis armato, 1.5-1.8 cm. longo, 

 circum 8 mm. crasso; rostris infra crassis et validis, ad basim glanduloso- 

 pubescentibus, ad medium plerumque inflexis, ad apicem plus minusve 

 hamosis, 3-5 mm. longis; aculeis rectis, ad basim glandulosis aut ranter 

 pubescentibus, aliter glabris, ad apicem hamosis, 4-6 mm. longis; 

 rostris et aculeis plerumque purpureo-tinctis, praesertim versus apicem. 



DISTRIBUTION: California. 



SPECIMENS EXAMINED: CALIFORNIA: vicin. of Palo Alto, foothills, 

 C. F. Baker 1760 (Hb. Calif. 131236, type; Hb. Field 226601; Hb. Gray; 

 Hb. Mo. 85385; Hb. N. Y.); Neponset, Salinas River, L. R. Abrams 

 4023 (Hb. Calif. 149139); West Berkeley, Harriet A. Walker 478 (Hb. 

 Calif. 130051). 



1 It may be remarked that the type of X. crassifolium Millsp. and Sherff (Field 

 Mus. Bot. 4: 5. 1918) was collected at San Antonio, not far from Bexar, in Bexar 

 County, Texas. The two plants show a close resemblance, but the Berlandier plant 

 is much thinner-leaved and less scabrous. We are disposed to consider X. crassifolium 

 as probably a variety or race of X. pennsylvanicum, a conclusion that we have 

 reached also in the case of X. acutilobum Millsp. & Sherff (he. cit., p. 6). Since de- 

 scribing X. crassifolium (Field Mus. Bot. 4:4. 1918) we have found several somewhat 

 intermediate herbarium specimens. One of these, C. L. Shear 220, vicin. of Osborne 

 City, Kansas, Aug. 27, 1894 (Hb. Gray), has the coarse, highly scabrous stem and 

 leaves of X. crasstfolium, but the leaves are large, as in X. pennsylvanicum. 



J At various times in later years, Dr. Greene erroneously determined certain 

 specimens of Xanthium as representing his X. californicum. These belonged to 

 X. pennsylvanicum, X. calvum, etc. Greene's own type specimen of X. califor- 

 nicum was, as stated above, the same form as that collected by W. L. Jepson, Oak- 

 land, California, Oct. i, 1894 (Hb. Mo. 85387), a form of X. pennsylvanicum. 



