FLOWERING PLANTS AND FERNS OF ARIZONA 503 



56. PHASEOLUS. 7 * Bean 



Plants herbaceous, annual or perennial, often with very large roots; 

 stems usually long and trailing or weakly twining; leaves pinnately 

 3-foliolate, with stipels; flowers axillary, mostly in racemes; corolla 

 purplish pink to deep purple, or brick red, the keel strongly curled 

 or spirally coiled; pods flat, linear to broadly ovate or obovate in out- 

 line, completely dehiscent; seeds rounded, rather large. 



Several exotic species are widely cultivated for human food, notably 

 the common or string bean (P. vulgaris) and the lima bean (P. lunatus). 

 The scarlet-runner (P. multiflorus) is often grown as an ornamental 

 climbing plant. All of the native beans improve the soil, make a good 

 ground cover, and provide excellent forage for livestock. The form 

 of P. acutifolius known as tepary bean is grown to such an extent by 

 the Papago Indians that they have been nicknamed "bean people," 

 and it also is planted by white farmers in the Southwest both for the 

 beans and for increasing the fertility of the soil. P. metcalfei produced 

 abundant forage in an experimental planting in Xew Mexico. The 

 beans of this and probably other species were eaten by the Apache 

 Indians. 



Key to the species 



1. Flowering stems from a deep-seated, globose tuber, erect or slightly twining, 

 seldom more than 30 cm. long; calyx not subtended by bractlets (bracts 

 present at base of the pedicel only) : leaflets lanceolate, entire, less than 1 

 cm. wide: peduncles 1- or 2-flowered; corolla purple, 15 to 20 mm. long; 



pods linear, 2.5 to 3.5 cm. long 1. P. parvulus. 



1. Flowering stems not from a globose tuber, trailing or twining, usually more 

 than 30 cm. long; calyx subtended by a pair of bractlets, these often 

 deciduous long before anthesis (2). 

 2. Plant annual, the root not thickened; steins, leaves, and pods sparsely short- 

 pilose, puberulent, or glabrate: leaflets linear and nearly entire to 

 triangular-lanceolate or ovate and very shallowly subhastately lobed on 

 one or both sides; corolla pale purple or purplish pink: pods 3 to 7 cm. 

 long, 4 to 10 mm. wide, somewhat abruptly slender-tipped. 



2. P. ACUTIFOLIUS. 



2. Plants perennial, with a thick, more or less woody, elongate root (3). 

 3. Pods linear, less than 5 mm. wide (4). 



4. Pubescence soft, often very dense, the hairs mostly appressed; leaflets 

 nearly entire to deeply lobed: corolla deep purple, 15 to 20 mm. long; 

 pods usually spreading, 6 to 10 cm. long, 3 to 4.5 mm. wide, gradu- 

 ally long-acuminate 3. P. ATROPURPUREUS. 



4. Pubescence villous or subhirsute, the hairs spreading or retrorse; 



corolla brick-red, drying purplish, not more than 15 mm. long; pods 

 reflexed, not more than 3 cm. long and 3 mm. wide. 



4. P. HETEROPHYLLUS. 



3. Pods broader than linear, commonly more than 5 mm. wide; stems and 

 petioles puberulent, short-pilose, or glabrate: corolla pink or purple (5). 



5. Leaflets broadly rounded-ovate, entire or very nearly so, the veins 



reticulate and somewhat prominent beneath; corolla deep rose purple; 

 seeds smooth or nearly so (6). 

 6. Pods 7 to 10 mm. wide, short-stipitate: bractlets 1 mm. long or 



shorter 5. P. ritexsis. 



6. Pods 12 to 18 mm. wide, sessile or nearly so; bractlets 1.5 mm. long 



or longer 6. P. metcalfei. 



5. Leaflets linear to triangular-ovate or, if broader, then deeply lobed, the 

 veins not noticeably reticulate and prominent beneath: corolla 

 purplish pink: seeds irregularly rugose: pods not more (usually less- 

 than 8 mm. wide, commonly broadest above the middle (7). 



:i Reference: Piper. C. V. studies i.v American" phaseouxeae. Contrib. U. S. Natl. Herbarium 

 663-701. 1926. 



