Astragalus helleri Fenzl
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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(2): 597-1188.
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Family
Fabaceae
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Scientific Name
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Type
"Am trachytischen Sandbogen am Westabhange der Cordillera des Orizaba zwischen 9-10,000' uber d. M., unweit des Rancho Canoitas auf dem selten betretenen Gebirgspass, welcher von Capilla nach Achilchotla fuhrt...Heller, Pl. Mex. 236."—No typus examined, b
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Synonyms
Tragacantha helleri (Fenzl) Kuntze, Astragalus orthanthus A.Gray, Tragacantha orthantha (A.Gray) Kuntze, Astragalus erythrostachys Ulbr.
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Description
Species Description - Robust, bushily tufted perennials, with stout taproot and stems at length indurated at base, densely silky-tomentose with shorter, curly, and longer, ascending, spirally twisted hairs up to 0.8-1.3 mm. long, the herbage white when fresh but the vesture turning rusty when dry; stems several or numerous, diffuse or ascending, up to 2 dm. long, branched or spurred at several nodes below the middle or almost simple, densely leafy, the internodes usually not much over 1-2 cm. long; stipules 3-10 mm. long, broadly triangular-apiculate or lanceolate, semi- amplexicaul-decurrent, densely pubescent dorsally; leaves 8—25 cm. long, with thick, ultimately stiff petioles and (19) 23-35 obovate-elliptic, or oval, obtuse or penicillate-acute, flat or loosely folded leaflets 4—12 mm. long; peduncles stout, erect or incurved-ascending at anthesis, apparently reclinate in fruit, up to 16 cm. long; racemes shortly but loosely 10-20-flowered, the flowers ascending, the axis 3.5-7 cm. long in fruit; bracts firm, lanceolate, 2-5 mm. long; pedicels ascending, at anthesis 1-2.5 mm., in fruit greatly thickened and up to 5 mm. long; bracteoles 0; calyx 12.5-18 mm. long, densely tomentose like the foliage, the subsymmetric disc 2-2.5 mm. deep, the cylindric, reddish tube 8.5-13 mm. long, 4-4.5 mm. in diameter, the subulate or lance-subulate teeth 2.5-6 mm. long, the whole becoming papery, ruptured, but apparently not circumscissile; petals scarlet, drying crimson; banner nearly erect, oblanceolate, 25-33 mm. long, 6-8 mm. wide, the midvein running out at the acute apex as a mucro about 0.5 mm. long; wings 23-28 mm. long, the claws 13-17 mm., the narrowly lanceolate, acute, nearly straight blades about 11-12.5 mm. long, 1.5-3 mm. wide; keel 22-27 mm. long, the claws 14-18 mm., the oblong, acute, slightly incurved blades 9-11 mm. long, 2-3 mm. wide; pod (seldom seen) somewhat obliquely oblong-ellipsoid, at least 2.5 (reportedly up to 5) cm. long, 1 cm. or more in diameter, broadly cuneate or rounded at base, contracted at apex into a short point, a little obcompressed, sulcate dorsally, the slightly fleshy, at length stiffly papery, stramineous, reticulate valves densely tomentulose, inflexed (through the pod’s lower ?) as a complete septum at least 3 mm. wide; ovules ± 29-36; dehiscence and seeds unknown.
Distribution and Ecology - On dry banks among rough grasses and shrubs, on volcanic sandy hillsides, sometimes at the edge of pine woods, 7000-10,400 feet, apparently quite local, known only from the slopes of Mt. Orizaba and vicinity, Puebla and Vera Cruz.— Map No. 100.—April to September.
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Discussion
The Orizaba milk-vetch, A. Helleri, is a spectacular astragalus. In habit of growth the species closely resembles some of the more robust, caulescent phases of A. mollissimus, but the greatly elongated flower with its narrow, acute, almost erect petals is most distinctive. In fact, the flowers suggest an Erythrina in their peculiar shape and brilliant scarlet coloring, and are shown off to the greatest possible advantage by the dense, silky-tomentose vesture of the stems and leaves. In a note on the red-flowered Mexican species (Barneby, 1956, p. 501) A. Helleri was associated with A. sanguineus, and it was suggested that the two species formed a section of their own. The arrangement seemed a natural one, but at the time the pod of A. Helleri was kown only from immature specimens and from descriptions of plants cultivated in Europe. Fenzl likened the pod to that of A. mexicanus (our A. crassicarpus var. Berlandieri), and I wrongly assumed that, like that of A. sanguineus and other Sarcocarpi, it was succulently fleshy becoming pithy when ripe. As shown by examples collected recently by Balls & Gourlay (cited above), the pod is in reality of quite thin texture, becoming stiffly papery when mature. Thus, except for the long, red flower, A. Helleri has every character, including the characteristic pubescence which tarnishes on drying, of sect. Mollissimi, whereas A. sanguineus, granted the same reservation about the flower, is a typical member of sect. Sarcocarpi. Apparently these two Mexican species and the Californian A. (Argophylli) coccineus have arisen independently from three separate evolutionary branches of the genus. It is remarkable that the modification in flower-color has occurred in each along with a modification of the petal-shape. In all three species the scarlet petals are held nearly erect out of the calyx, forming the nearest approximation to a tubular perianth which the papilionaceous flower can acquire. They are typical hummingbird flowers, but whether birds play any role in their fertilization is unknown.
No authentic material of A. Helleri or A. erythrostachys has been examined, but the descriptions are unusually full and explicit, the tomentose pubescence of the leaves and the distinctive shape, color, and great length of the petals being stressed. All three names cited in the synonymy were based on plants collected on the slopes of Mt. Orizaba, and there can be no reasonable doubt that they refer to the same species. The foregoing description will need amplification as more is learned about variation in the fruit. Fenzl described it as reaching a length of two inches ( ± 5 cm.), about twice as long as any found in American herbaria today.
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Objects
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Distribution
Puebla Mexico North America| Veracruz Mexico North America|