FLOWERING PLANTS AND FERNS OF ARIZONA 499 



5. Vicia exigua Nutt. ex Torr. and Grav, Fl. North Amer. 1: 272. 



1838. 

 Mohave County to Greenlee, Gila, Pinal, Maricopa, Pima (and 

 probably Yuma) Counties, 4,000 feet or lower, common among bushes 

 on slopes and in canyons, March to May. Western Texas to Oregon 

 and California. 



50. LATHYRUS. Peavixe 



Plants perennial, herbaceous; stems erect or weakly climbing; 

 leaves pinnate, commonly ending in a tendril, the leaflets usually 

 fewer, larger, thicker, and more prominently veined than in Vicia; 

 stipules large and conspicuous; flowers large and showy, commonly 

 in axillary racemes, the corolla purple to nearly- white; pods much as 

 in Vicia. 



The best-known member of this genus is the sweet pea (L. odoratus), a 

 native of Sicily. The native species of Arizona bear a general resem- 

 blance to this favorite of gardens. Apparently the plants are less 

 palatable to livestock than are the vetches. 



Key to the species 



1. Tendrils none or very rudimentary; corolla white or whitish, 10 to 15 mm. 

 long; stems erect or nearly so; leaflets usually 4, linear, lanceolate, or 

 narrowly elliptic, 2.5 to 6 cm. long, 4 to 20 times as long as wide. 



1. L. ARIZOXICUS. 



1. Tendrils well developed; corolla normally purple or purplish pink (2). 



2. Flowers commonly more than 2 cm. long; stems usually erect; tendrils com- 

 monly simple; stipules usually erect or ascending; leaflets thickish, 

 veiny, elliptic or lanceolate (exceptionally linear-lanceolate), 2.5 to 5 



cm. long, 4 to 8 times as long as wide 2. L. 'eucosmus. 



2. Flowers less than 2 cm. long; stems more or less climbing; tendrils simnle 

 or forked; stipules usually spreading or reflexed (3). 

 3. Leaflets narrowly linear to almost filiform, 3 to 10 cm. long, seldom more 

 than 5 mm. wide, 9 or more times as long as wide; tendrils often sim- 

 ple 3. L. GRAMIXIFOLIUS. 



3. Leaflets oval, rhombic-elliptic, or oblong-lanceolate, 2 to 5 cm. long, 6 

 to 20 mm. wide, 2 to 6 times as long as wide; tendrils commonly 

 forked 4. L. parvifolius. 



1. Lathyrus arizonicus Britton, X. Y. Acad. Sci. Trans. 8: 65. 1889. 

 Apache County to Coconino County, south to Graham and Pima 



Counties, 6,500 to 11,000 feet, chiefly in coniferous forests, May to 

 October, type from the Mogollon Escarpment, Coconino County 

 (Mearns 57). Colorado, Xew Mexico, and Arizona. 



2. Lathyrus eucosmus Butters and St. John, Rhodora 19: 160. 1917. 



Lathyrus decaphyllus of authors. Probably not Pursh, 1814. 



Apache, Navajo, and Coconino Counties, 5,000 to 7,000 feet, 

 often in open dry woods of pinyon and of yellow pine, May to August. 

 Nebraska to Utah, New Mexico, and northern Arizona. 



A handsome plant, with larger and showier flowers than in any other 

 of the Arizona species. Its habit of spreading by horizontal root- 

 stocks makes it a useful soil binder. 



