Astragalus guatemalensis var. brevidentatus (Hemsl.) 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
Astragalus guatemalensis var. brevidentatus (Hemsl.) Barneby
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Type
"Mexico, (Barker). Cultivated specimens only in Hb. Kew."—Holotypus, cult, in hort. Kew. Aug. 13, 1838, K!
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Synonyms
Astragalus strigulosus var. brevidentatus Hemsl., , Astragalus guatemalensis var. oaxacanus M.E.Jones, Atelophragma oaxacanum (M.E.Jones) Rydb., Astragalus oaxacanus (M.E.Jones) Rose ex M.E.Jones, Astragalus painteri M.E.Jones, Atelophragma painteri (Rose ex M.E.Jones) Rydb.
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Description
Variety Description - Like var. guatemalensis in growth-habit, the stems 3-15 (24) dm. long; leaflets (13) 17-25; racemes shortly but more loosely 6-20 (30)-flowered, or those of terminal branchlets only 2—5-flowered. the axis (0.5) 1.5-3.5 (5) cm. long in fruit; calyx strigulose with black, rarely white hairs up to ± 0.2-0.3 mm. long, the tube 2.6-3.6 mm. long, 2.2-3 mm. in diameter, the triangular-subulate, broadly deltoid, or more elongate and then truly subulate teeth 0.6-2.5 mm. long; petals commonly pink-purple, rarely yellowish; banner 9-11.3 mm. long; stipe of the pod 1.5-2.5 mm., the body 12-21 mm. long, (4) 5-7 (8) mm. in diameter, glabrous or minutely black-strigulose; ovules (11) 12-18 (19).
Distribution and Ecology - Brushy hillsides, open woodland, and shaded glens in mixed pine and oak forest, (5500) 6000-8500 feet, apparently not uncommon in the mountains of southcentral Mexico, from Mexico State to Michoacan and western Jalisco, south to Oaxaca.—Map No. 7.—May to January.
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Discussion
The Oaxaca milk-vetch, var. brevidentatus, is the commonest and most widely dispersed in southcentral Mexico of the large-flowered Strigulosi. Similar to var. guatemalensis in the diffuse vinelike habit of growth and in nearly all technical characters other than the shorttoothed, more thinly appressed-pubescent calyx, it is geographically separated from it by the dip in the main Cordillera corresponding with the Isthmus of Tehuantepec. The variety is so circumscribed in these pages as to include a number of minor variants; it could perhaps be divided profitably into two coordinate races corresponding with Jones’s var. oaxacanus and A. Painteri. In the mountains lying between the valleys of Mexico and Cuernavaca the calyx-teeth are consistently very short, scarcely surpassing 1 mm. in length, and vary from broadly subulate to broadly deltoid, the typi of A. Painteri and var. brevidentatus being of the latter sort. To the west and south of this area the calyx-teeth become longer and narrower, varying from broadly subulate to exactly subulate, and from 1 mm. up to 2.5 mm. in length; however there seem to be no other differences correlated with the calyx-variants. The pod of the Oaxaca milk-vetch is most commonly glabrous, but a number of collections with minutely black- strigulose fruits are on record: several from Michoacan (Frye & Frye 3105; Hinton 15,465, both US; Ripley & Barneby 13,432, both CAS, NY, RSA) one from Guerrero (Hinton 14899, MICH, NY, UC); one from Oaxaca (the typus of var. oaxacanus); and the original plant from which var. brevidentatus was described. These pubescent-ovaried plants are interpreted as individual variants of no taxonomic importance. The petals of var. brevidentatus are normally pinkish-purple, but they fade rapidly in the herbarium, often appearing ochroleucous after a few years; and ochroleucous or "pale yellow" flowers have been seen and reported in field notes (Hinton 15,465, US) as well as the commoner purple.
During the preliminary studies, before the identity of var. brevidentatus had been established, I annotated many sheets of this variety as var. oaxacanus Jones.
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Objects
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Distribution
Jalisco Mexico North America| Michoacán Mexico North America| México Mexico North America| Morelos Mexico North America| Oaxaca Mexico North America|