FLOWERING PLAXTS AXD FERNS OF ARIZONA 795 



10. Leaf blades deeply pinnatifid. with acute, triangular segments; 

 plant annual, the pubescence appressed, almost scurfy; stems 

 strongly decumbent or prostrate; cymes 1- to 3- (commonly 2-) 

 flowered; corolla less than 10 mm. in diameter; berry green at 



maturity 10. S. triflorum. 



10. Leaf blades entire to sinuate-dentate (11). 



11. Plant perennial, often suffrutescent, sparsely to densely cinere- 

 ous-puberulent or short-pilose, the hairs mostly appressed or 

 subappressed; corolla 10 to 18 mm. in diameter; berry com- 

 monly black at maturity 11. S. DOUGLASII. 



11. Plant annual; corolla not more than 8 mm. in diameter (12). 

 12. Stems and leaves viscid-villous; berry yellow at maturity. 



12. S. VILLOSUM. 



12. Stems and leaves sparsely puberulent, strigose, or glabrate; 

 berry black at maturity 13. S. nigrum. 



1. Solanum rostratum Dunal, Solan. Syn. 234. 1813. 



Androcera rostrata Rvdb., Torrev Bot. Club Bui. 33: 150. 

 1906. 



Apache County to Coconino County, south to Cochise and Pima 

 Counties, 1.200 to 7,000 feet, common on plains and at roadsides in 

 the northern part of the State, perhaps introduced from farther east, 

 July and August. North Dakota and Wyoming to Arizona and 

 Mexico. 



Buffalo-bur. This species, believed to be the original host of the 

 Colorado potato beetle, is considered a pest in range land. 



2. Solanum heterodoxum Dunal, Hist. Solan. 235. 1813. 

 Kirkland, Yavapai County (Peebles et al. 7422), 4,000 feet, abun- 

 dant at roadsides, October. Western Texas to Arizona and Mexico. 



The form occurring in Arizona is var. riejvomexiearmm Bartlett 

 (Anelrocera novomexicana Woot. and Standi.), which is described as 

 being more densely pubescent and more spiny, and as having a larger 

 corolla and stamens, than in typical S. heterodoxum. It is stated 

 that the spines are brownish yellow in the variety, olivaceous in the 

 typical form. 



3. Solanum lumholtzianum Bartlett, Amer. Acad. Arts and Sci. 



Proc. 44: 629. 1909. 



Patagonia, Santa Cruz County (Harrison and Fulton 8185), near 

 Arivaca, Pima County (Kearney and Peebles 13775), 3.200 to 4.000 

 feet, sandy soil at roadsides, August to October. Southern Arizona 

 and northern Sonora. 



The plants are about 0.6 m. (2 feet high), with long widespreading 

 branches. 



4. Solanum sisymbriifolium Lam., Tabl. Encyl. 2: 25. 1793. 

 Near the Boyce-Thompson Southwestern Arboretum, Superior, 



Pinal County (McLellan), perhaps not established. Adventive from 

 tropical America. 



The leaves resemble those of the watermelon. 



5. Solanum elaeagnifolium Cav., Icon. PL 3: 22. 1794. 



Navajo County to Cochise and Pima Counties. 1,000 to 5,500 feet. 

 fields and roadsides, May to September. Kansas and Colorado to 

 Arizona and California, south to tropical America. 



White (or silver) horsenettle, bullnettle, trompillo. A troublesome 

 weed in irrigated land, especially in the southern counties, difficult 



