Astragalus kentrophyta var. implexus (Canby) Barneby
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
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Family
Fabaceae
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Scientific Name
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Type
"South Park, Canby; Hoopes; Porter."—Lectotypus, collected in South Park in August, 1871, by William M. Canby, NY (herb. Canby.)! isotypus, US!
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Synonyms
Astragalus tegetarius var. implexus Canby, Astragalus tegetarius S.Watson, Tragacantha tegetaria (S.Watson) Kuntze, Homalobus tegetarius (S.Watson) Rydb., Astragalus montanus var. tegetarius (S.Watson) M.E.Jones, Astragalus tegetarius var. rotundus M.E.Jones, Astragalus kentrophyta var. rotundus (M.E.Jones) M.E.Jones, Astragalus montanus var. rotundus (M.E.Jones) M.E.Jones, Kentrophyta rotunda (M.E.Jones) Rydb., Astragalus aculeatus A.Nelson, Kentrophyta aculeata (A.Nelson) Rydb., Homalobus wolfii Rydb., Kentrophyta wolfii (Rydb.) Rydb., Kentrophyta minima Rydb.
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Description
Species Description - Prostrate, the stems closely and repeatedly forking to form densely, more rarely loosely woven mats or soft, low-convex cushions 0.5-4 (5) dm. in diameter, the internodes often shorter than the stipules, or some of them developed and up to 5-18 mm. long, the herbage usually flaccid, becoming rigid and prickly only in some populations at low elevations late in the season or in the mountains of central Utah; stems and herbage cinereous, canescent, or greenish, densely to quite thinly strigulose, villosulous, or rarely villous, the hairs all or largely straight and subappressed, or ascending and either straight or sinuous, or some (all) loosely spreading, the longest up to 0.3-1 (1.2) mm. long, the leaflets pubescent on both sides, more rarely glabrous or medially glabrescent above; stipules 2-7 mm. long, the lower ones shorter and more fully connate than the upper ones of the year’s growth-cycle, the free blades lanceolate or lance-acuminate, neither rigid nor spinulose; leaves (2) 4-15 (20) mm. long, with (3) 5-9 leaflets 1-9 mm. long, these usually crowded, the rachis (0.5) 1.5-4 (7) mm. long, the terminal mucro or spinule (0.2) 0.5-1 (1.5) mm. long, scarcely vulnerant; peduncles subobsolete or up to 1.5 (3) cm. long; calyx (2) 2.4-5.7 (7) mm. long, the tube 1.2-2.6 (2.8)mm. long, 1.1-2.7 mm. in diameter, the subulate or subulate-setaceous teeth (0.5) 1.9-2.6 (4.2) mm. long; petals commonly purple or purplish, sometimes white with pink or purplish keel-tip; banner obovate-cuneate, flabellate, or broadly elliptic-obovate, (3.9) 4.5-8 (9.2) mm. long, 3.2-5.6 mm. wide; wings (3.8) 4.4-7.4(8.1) mm. long, the claws (1) 1.2-2.5 (2.7) mm., the blades (3.1) 3.5-5.5(6.1) mm. long, 2.1-2.4 mm. wide; keel 2.9-6 (6.3) mm. long, the claws 1-2.6 (2.8) mm., the blades 2-3.9 (4.2) mm. long, 1.3-2.2 mm. wide; pod ellipsoid or oblong-ellipsoid, subsymmetric, (3) 4-8 (9) mm. long, (1.6) 2-2.5 mm. in diameter; ovules 5-8, rarely 4 or 3 in some flowers.
Distribution and Ecology - Rocky slopes and crests near and above timber line, descending on gravel slides, open stony hillsides, and talus to barren knolls and benches in the forest and sagebrush zones, mostly between 7500 and 12,000 feet, but coming out to the east foothills of the Rocky Mountains as low as 5000 (Big Horn Mountains, Wyoming) or even 3800 feet (east of Glacier Park, Montana), in soils of various types but mostly on limestone northward and westward and on granites in Colorado, widespread and locally plentiful in the Rocky Mountains from northwestern Montana to extreme northern New Mexico (becoming rarer southward), west to the Wallowa Mountains, northeastern Oregon, and on scattered mountain tops through the Basin Ranges of Utah and Nevada to the White Mountains in east- central California.—Map No. 37.—June to September.
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Discussion
The mountain kentrophyta, var. implexus, is variable in the length and orientation of the hairs on the leaves and stems, in the size and color of the flowers, and in the relative flaccidity or rigidity of the plant-body, especially of the leaflets. The firmness of the plant- tissues appears to be correlated with habitat. Flower-color is at least largely correlated with elevation, for the populations at and above timber line, particularly northward, have petals of a brighter pink- or violet-purple than those at middle elevations, but there are several exceptions to this rule on record. Study of the flower-color and of the comparative rigidity of the leaflets or length of the terminal spinule has shown only feeble correlation with natural patterns of dispersal, but size of the flower and type of vesture do reveal the existence of incipient racial differentiation. The largest flowers are found in the Rocky Mountains northward from the Red Desert in Wyoming; the smallest occur mostly in Colorado and on isolated mountain ranges within and bordering the Great Basin. It would be interesting to learn whether the few small-flowered plants which have been collected in the northern area, such as the typus of K. minima from Yellowstone Park and others like it from the headwaters of the Salmon River in Idaho, are truly representative of fixed populations or merely individual variants from particularly exposed habitats, as their generally condensed and thrifty habit of growth suggests. If such were so, it might be reasonable to distinguish a large-flowered northern "aculeatus" from a southern "tegetarius-implexus". Disregarding these few northern exceptions, I can bring out the following contrasting flower-measurements (in mm.):
Northwest Wyoming to Oregon and Montana
Calyx 3.2-5.7 (7)
Calyx-teeth 1.6-2.6 (4)
Banner 5.2-9.2
Keel 3.9-6.3
Colorado to New Mexico and California
Calyx 2.4-3.4
Calyx-teeth 0.5-1.5
Banner (3.9) 4.5-5.6 (6.2)
Keel 2.9-4
In spite of some overlap, the means of variation in the northern and southern Rocky Mountains are substantially different.
In the whole area to the north and west of the Grand-Arkansas watershed in central Colorado, the hairs of the herbage, whether spreading or appressed, are relatively short, the longest 0.3-0.7 mm. long. About the head of the Arkansas and South Platte, especially in South Park, and extending south to Cochetopa Pass in Saguache County and to the Red River canyon in Taos County, New Mexico, the hairs are consistently longer, up to 0.7-1.2 mm. long, the herbage becoming villous-canescent in the extreme state. The epithets implexus and Wolfii were originally applied to plants of this nature.
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Objects
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Distribution
Wyoming United States of America North America| Montana United States of America North America| Colorado United States of America North America| Oregon United States of America North America| New Mexico United States of America North America| Utah United States of America North America| Nevada United States of America North America| California United States of America North America| Idaho United States of America North America|