Dalea mucronata

Title

Dalea mucronata

Author(s)

Rupert C. Barneby

Scientific Name

Dalea mucronata DC.

Description

99.  Dalea mucronata DeCandolle

(Plate XCII)

Tall, coarse herbs with (1) 2-several erect or virgately ascending, smooth or striate, reddish stems 1-1.8 m tall, becoming indurated basally late in the season but not persistent in the form of a caudex, simple and leafy to the middle or beyond, then branched and sparsely tuberculate distally, the foliage much reduced in the inflorescence which forms a loose panicle of spikes, either wholly glabrous up to the spikes or the upper leaves thinly pubescent dorsally in youth, but the stems sometimes bearing late in the dry season short, subbasal spurs bearing reduced leaves with 2-3 pairs of densely white-pilose leaflets; leaf-spurs very short or obscure; stipules narrowly lance-acuminate to linear-elliptic, firm, foliaceous, 5-14 mm long, with rigid midrib, punctate dorsally; intrapetiolular glands 2, prominent, like the post-petiolular glands conic or prickle-shaped; main cauline leaves 4-8.5 cm long, with very narrowly margined rachis and 7-13 (15) pairs of ovate- or oblong-elliptic, basally subcordate to broadly rounded, apically short-acuminate (quasi-mucronate), dorsally carinate, flat leaflets 6-15 mm long, smooth and green above, strongly multipunctate beneath, the distal rameal leaves similar but shorter, with fewer (3-7) pairs of smaller but otherwise similar leaflets; peduncles 0.5-10 cm long (often appearing longer due to suppression of ultimate leaves); spikes very dense, subglobose or ovoid becoming ovoid-oblong to short-cylindroid, without petals 8-10 mm diam, the villosulous axis 0.5-5 cm long; bracts persistent, ovate-acuminate or -caudate, 3-5.5 mm long, cymbiform and embracing base of calyx, the lowest glabrous dorsally, the rest pilosulous externally in the lower half, livid-glandular and ciliolate distally, all silky within; calyx 3.9-4.9 mm long, glabrous externally except for a crest of short, spreading hairs extending backward from the ± recessed dorsal sinus, the campanulate tube 2.5-3 mm long, thick-textured, pallid or livid-castaneous and lustrous externally, the ribs immersed, the intervals poorly differentiated in texture and eglandular, the subulate or triangular-subulate teeth up to 1.2-1.8 mm long, the dorsal one longest, the ventral pair shortest and broadest, the orifice oblique, the teeth all minutely gland-spurred; petals greenish-white or ochroleucous, the banner early fading dull pinkish-red, all glandless, the inner ones perched ± 2.4-3.1 mm above the hypanthium rim, the keel- blades united by their outer margins; banner 4.6-5.5 mm long, the claw 2.4-2.8 mm, the cordate blade 3.1-3.5 mm long, 2.4-3.2 mm wide; wings 4.2-5 mm long, the claw 0.8-1.3 mm, the blade 3.5-4 mm long, 1.6-2.2 mm wide; keel 4.8-5.4 mm long, the claws 1.3-1.6 mm, the broadly obovate-elliptic blades 3.6-4.5 mm long, 2-2.5 mm wide; androecium 6-7.5 mm long, the longest filament free for ± 2.7 mm, the connective gland-tipped, the anthers 0.65-0.8 mm long; pod in profile obliquely deltate, 2.2 -2.5 mm long, the ventral suture slightly convex, the dorsal suture and prow filiform, the valves hyaline in lower half, thence thinly papery, thinly pilosulous distally or merely ciliolate below the style; seed 1.6-1.8 mm long; 2n = 14 (Mosquin). — Collections: 15 (v).

Dry rocky hillsides and valley-floors, in arid grassland, ipomoea forest, and thin oak woodland, 1500-2700 m (± 5000-9000 ft), uncommon and occurring usually as scattered individuals, thinly dispersed around the foothills, in valleys of Rio Lerma and its affluents from the n., from Guadalajara, Jalisco, n. to s. Zacatecas and Aguas Calientes, upstream through the Bajio and the lake-basins of n.-e. Michoacan to n.-e. Guanajuato and, perhaps disjunctly, to the Valley of Mexico. — Flowering September to November .—Representative: Zacatecas: road to Huejuquilla El Alto, McVaugh 16,907 (MICH). Jalisco: n.-w. of Huejuquilla El Alto, Feddema 2376 (MICH); 17 mi n.-w. of Lagos de Moreno, Ripley & Barneby 14,516 (CAS, DAO, MEXU, NY); Guadalajara, Pringle 2353 (BR, F, M, MEXU, NY, UC, W). Aguas Calientes: 10-20 mi w. of Aguas, McVaugh & Koelz 86 (MICH). MichoacAn: 24 km w. of Morelia, Ripley & Barneby 14,848 (CAS, DAO, GH, MEXU, MICH, NY, US); 7 mi e. of Quiroga, Ripley & Barneby 13,426 (MEXU, NY); 3 mi s.-e. of Quiroga, Breedlove 18,704 (NY). Guanajuato: 13 mi w. of Dolores Hidalgo, Ripley & Barneby 13,375 (CAS, NY, US). Mexico (Edo): Lecheria, Pringle 8917 (K, L, M, MEXU, NY, UC, US, W). Mexico (D. F.): Cerro de Progreso, Matuda 19,672 (MEXU, NY).

Dalea mucronata (mucronate, of the leaflets) DeCandolle, Prod. 2: 246. 1825. —"...in Mexico." —Holotypus, "ex herb. Thibaud., 1815", G-DC! Parosela mucronata (DC.) Rose, Contrib. U. S. Nat. Herb. 10: 104. 1906.

Dalea aristata (bristle-tipped, of the pointed leaflets) Bentham, Pl. Hartweg. 11. 1839.—No locality given; Graham collected around Mexico City and in the mining districts of Tlalpuxahua and Real del Monte. — Holotypus, Graham in 1830, K!

Among herbaceous daleas D. mucronata is a giant, its stout red virgate stems, solitary in young plants but later several together, bearing aloft from one to almost two meters high their narrow panicles of disproportionately small heads. Its great stature, long stipules, ample short-acuminate leaflets of thick texture, densely conelike spikes of small shiny short-toothed calyces subtended by persistent, internally silky bracts, and its small, dingily ochroleucous petals all contribute to a unique facies. Rydberg (1920, p. 94) described Parosela mucronata as glabrous, but the plants are only rarely hairless when closely examined. The typus, part of a young plant with flowers not yet expanded, has thinly but obviously pubescent upper leaves, and. traces of pubescence can be found in almost all specimens collected since. Densely pilosulous innovations arising late in the year from the base of main stems otherwise almost glabrous, reveal a latent potentiality for developed vesture. So far as known the calyx is always glabrous externally except for a crest of short hairs around the recessed dorsal sinus, but its mouth is silky-fringed within.

The typus of D. aristata Benth., a species overlooked by Rose and Rydberg, is characteristic. A record of D. mucronata from southwest Chihuahua (Gentry, 1942, p. 139) is based on a collection (Gentry 2838) of D. leucostachya var. eysenhardtioides.