FLOWERING PLANTS AND FERNS OF ARIZONA 493 



cence and few-jointed pods (segments 3 or 4). The roots are thickly 

 beset with bacterial nodules. 



46. STYLOSANTHES. Pexcilflower 



Perennial herbs; leaves digitately trifoliolate, with sheathing stip- 

 ules, the leaflets conspicuously veined; flowers small, in interrupted 

 terminal spikes with leaflike bracts, or some axillary, the corolla 

 yellow; fruit (loment) of 2 segments, the terminal one reduced and 

 infertile, dehiscent at apex, tipped by the persistent hooked style. 



*1. Stylosanthes biflora (L.) B. S. P., Prelim. Cat. N. Y. 13. 1888. 



TrifoHum biflorum L., Sp. PL 773. 1753. 



This species, of which the known range is from New York to Kansas, 

 Florida, and Texas, is included in the Arizona flora on the basis of a 

 specimen in the Gray Herbarium collected in " Arizona or Xew Mex- 

 ico" (IF. F. Parish 314) identified by M. L. Fernald as var. hispidis- 

 sima (Michx.) Pollard and Ball. 



47. ZORNIA 



Plants herbaceous, perennial; leaves 2-foliolate (in the Arizona 

 species), the stipules sagittate; flowers in axillary and terminal spikes 

 or some of them solitary in the axils; bracts very different from the 

 foliage leaves, paired, connivent, nearly enclosing the flower; corolla 

 orange yellow, the keel incurved; fruit (loment) flat, several-jointed. 



1. Zornia diphylla (L.) Pers., Syn. PI. 2: 318. 1807. 



Hedysarum diphyllum L., Sp. PI. 747. 1753. 



Cochise, Santa Cruz, and Pima Counties, 4,000 to 6.000 feet, dry 

 rocky slopes and mesas, August to October. Southern Arizona to 

 Central America. 



A form collected at Xogales, also occasional in Mexico and Central 

 America, has longer, much narrower, and longer-acuminate leaflets, 

 less prominently veined and more acuminate bracts, and less copious 

 pubescence than in the normal form of the species. 



48. DESMODIUM. 73 Tickclover 



Plants annual or perennial, herbaceous or suffrutescent ; stems erect 

 to prostrate; leaves 3-foliolate or (in a few species) reduced to 1 leaflet ; 

 flowers in terminal or axillary racemes, these simple or compound, the 

 corolla purplish pink or sometimes white; fruit (loment) flat, of 

 several 1-seeded segments, these all alike, indehiscent or nearly so. 



The name beggarticks is also sometimes used for these plants, 

 because the joints of the pods stick tightly to clothing and to the hair 

 of animals. There seems to be little evidence that the plants are 

 relished by livestock although, in view of the great abundance of some 

 of the species in Arizona and the presumable absence of any poisonous 

 or disagreeable constituent, they would seem likely to be important 

 range plants. Perhaps the fact that most of the species grow where 

 grasses are abundant and are at the height of their growth in late 



rs Reference: Schubert, Berxice G. desmodium: preliminary ^tvlue^. I. Contrib. Gray Herbarium. 



129: 3-31. 1940. 



