Lotus humistratus Greene

  • Authority

    Isely, Duane. 1981. Leguminosae of the United States. III. Subfamily Papilionoideae: tribes Sophoreae, Podalyrieae, Loteae. Mem. New York Bot. Gard. 25 (3): 1-264.

  • Family

    Fabaceae

  • Scientific Name

    Lotus humistratus Greene

  • Description

    Species Description - Prostrate or low-ascending, multi-stemmed, commonly mat-forming, strongly villous or slightly hairy, subsucculent annual .5-3 dm. Leafstalk flattened, nerved, 4-10 mm; leaflets (3-)4(-5), irregularly arranged, commonly 2 distal, the other 2 from one side of axis; blades elliptic or obovate, 4-12 mm, 1.3-3.2 r. Stipules inconspicuous glands. Flowers 5-9 mm, axillary, subsessile, usually solitary, sometimes twisted and appearing resupinate, congested amid leaves and pubescence. Calyx tube 1-2 mm, conspicuously pubescent; teeth (1.8—)2—4 mm, 1-2 r. Corolla yellow, turning red; standard remaining horizontal or ascending to 90°; wings ± keel. Ovary villous, with ca. 3 ovules; style abruptly defined, sinuously geniculate; stigma not penicillate. Legume ascending, broadly oblong, compressed, 6—12(—14) mm x 3-4 mm, less than 4 r, villous, persistent, dehiscent. Microlotus.

  • Discussion

    Hosackia brachycarpa Benth. (1848); Lotus brachycarpus Benth. & Hook. ex. Wats. (1878) non Hochst. & Steud. (1841); Anisolotus brachycarpus (Benth.) Rydb. (1906); L. humistratus Greene (1890). L. trispermus Greene (1893); A. trispermus (Greene) Woot. & Standi. (1913). 2n = 12 (Grant, 1965). Lotus humistratus is a common, mat-forming species with axillary, subsessile or sessile flowers and fruit. It is sympatric in California with its relative, L. wrangelianus from which it differs in its shorter, broad pod and longer calyx lobes. Variance, in the Arizona portion of its range, where L. wrangelianus does not occur, however, precludes consistent morphological differentiation. But since the two species commonly grow together in California with no sign of mingling, the conventional treatment seems reasonable. Possibly Lotus humistratus includes several varieties. The flowers of California L. humistratus from approximately Monterey co and north are usually larger (89 mm) than those of plants in southern California and Arizona (5-7 mm). In Arizona and New Mexico, some populations have reduced pubescence, and often longer pods and proportionately shorter calyx teeth than the species in California. The variant forms (L. trispermus Greene), however, have, seemingly, only random distribution among the “normal” types, and I regard them as elements of phenotypic diversity rather than evidence of a coherent variety. Both the isolated populations, in Idaho and Washington co, Utah, are glabrate, or slightly pubescent. Lotus humistratus, in favorable springs, forms carpets in the awakening desert, and may be seen along southern Arizona highway shoulders for miles on end. Blooming begins in middle March to April, and flower and fruit production continues until halted by summer drought and heat.

  • Distribution

    United States and adjacent Mexico. Cismontane California to s Oregon; e across s deserts to w New Mexico and sw Utah; disjunct in s Idaho. California: coast range grassland and scrub to middle elevations in the Sierra Nevada with oak and pine; serpentine, sand bars, rocky, open and disturbed areas. Deserts and east: low elevation, desert flats and washes to middle elevation mountains; creosote bush, grass-Agave-Prosopis, roadsides. Frequent and abundant. 0-5000 (-6000) ft. March-April (s), April

    United States of America North America| Mexico North America|