Monographs Details: Dalea carthagenensis var. isthmicola Barneby
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1977. Daleae Imagines, an illustrated revision of Errazurizia Philippi, Psorothamnus Rydberg, Marine Liebmann, and Dalea Lucanus emen. Barneby, including all species of Leguminosae tribe Amorpheae Borissova ever referred to Dalea. Mem. New York Bot. Gard. 27: 1-892.
Description:Species Description - Low, twiggy shrubs up to 6 dm tall, glabrous to the spikes, the young branchlets verruculose; main cauline leaves persistent into anthesis of spikes, 3.5-4.5 cm long, sessile, with ± 19-25 stiffly chartaceous, marginally subrevolute, oblong-elliptic leaflets 6.5-8 mm long; spikes appearing axillary to living leaves, in reality terminal to very short leafless axillary shoots, rather loosely ± 10-20-flowered, without petals ± 14-15 mm diam, the villosulous axis mostly 1-1.5 cm long; bracts elliptic, villosulous dorsally below middle, thence green, glabrate, charged with prominent blister- glands; calyx 6.5-7 mm long, villosulous all over with fine, spreading-ascending hairs up to 0.6-0.75 mm long, the tube ± 2.5 mm long, less densely and more shortly pubescent than the plumulose teeth, the intercostal glands ±3-4, prominent but small, the recurving teeth up to 4-4.6 mm long, the dorsal one obscurely sigmoid distally; petals opening greenish-creamy fading brownish-maroon; banner ± 5.3 mm long, the claw 2.4-2.7 mm, the blade 3.1-3.2 mm long, 3.4-3.7 mm wide; keel 6.7 mm long, the claws 2.2 mm, the blades 5 mm long, 2.9 mm wide; androecium ± 7 mm long.— Collections: 1 (o).
Distribution and Ecology - Brushy savannah country below 225 m (750 ft), known only from the type-locality near Chivela Pass on the continental divide of Isthmus of Tehuantepec, s.-e. Oaxaca.— Flowering November-December.
Latin Diagnosis - Dalea carthagenensis (Jacqu.) Macbr. var. isthmicola Barneby, var. nov., var. capitulatae (Rydb.) Barneby proxima sed statura humili, caulibus verruculosis, foliolis foliorum caulinorum majorum pluri (9-12, nec 4-7)-jugis, spicis laxius plurifloris (axi 10-15 nec 2-7 mm longo), necnon floris paullo majoris carinae lamina majori (± 5 nec 3.7-4.4 mm longa) recedens. - Oaxaca: between the railroad stations of Chivela and Nizanda on the trans-isthmus line, Isthmus of Tehuantepec, Dec 28, 1944, E. J. Alexander 191.
While reluctant to describe further varieties of D. carthagenensis, especially from only one collection, I feel obliged to provide a taxonomic niche for this distinct-looking plant. It appears to be most closely akin to var. capitulata, its relative nearest northward, which abounds in the arid valleys of central Oaxaca at elevations upward from 800 m. Features common to the two are the relatively small, firm leaflets, no doubt an adaptation to xeric habitat, and the reduction of the inflorescence to spikes sessile at the tip of very short axillary spurs along the branches of the current year. The var. isthmicola differs in its low stature, verruculose stems, numerous leaflets, and longer, looser spikes of rather larger flowers. The main cauline leaves of var. capitulata are commonly thrown off before the flowering spikes reach anthesis, but are persistent in var. isthmicola. Only the distantly allopatric var. floridana has as many pairs of leaflets; this is a taller plant, nearly always villosulous throughout, and has spikes central to each major division of the panicle elevated on a developed peduncle. The var. barbata, which represents the species in Central America from mountainous Chiapas southward, has flowers of the size of var. isthmicola but combined with leaflets at once fewer and larger, and in consequence a different aspect.
Oaxaca Mexico North America
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