Dalea confusa (Rydb.) 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.

Family

Fabaceae

Scientific Name

Dalea confusa (Rydb.) Barneby

Description

Species Description - Erect, slender, annual herbs, 1-4 dm tall, the angular-ribbed stems simple and monocephalous or, more commonly, few-branched from near the base or from near the middle, the branches mostly simple and 1 (rarely 2)-cephalous, not or sparsely punctate distally, appearing glabrous beneath the spikes but the leaflets charged along the margins with a few weakly spreading, spiral hairs, the foliage green, the leaflets somewhat leathery in texture, a little paler and punctate beneath; leaf-spurs 0.5-1.4 mm long; stipules triangular-acuminate to subulate, firm, brownish, (1) 1.5-3.5 mm long; intrapetiolular glands minute, spicular or conic; post-petiolular glands prominent; leaves subsessile, 0.8-3 cm long, with rather broadly margined, glandless rachis and 2-4 pairs of oblanceolate to oblong-elliptic, short-acuminate, subacute, or obtuse and mucronate, flat or marginally involute leaflets (3) 4-15 mm long, the terminal one longest, stalked beyond the last pair; peduncles 0.2-7 cm long; spikes very dense, conelike, ovoid to subglobose becoming ovoid-oblong, without petals 6-8 mm diam, the pilosulous axis 5-20 mm long; bracts persistent (shed only with the ripe fruit and calyx), subhomomorphic or the lowest sometimes longer than the rest, the interfloral ones 2.2-4.5 mm long, the body cuneate-flabellate, -obcordate, or oblanceolate, subtruncately contracted into a tail ± 0.8-2.5 mm long, membranous-margined proximally, glabrous and commonly charged with a few glands dorsally, ciliolate beyond the middle, the tip of the body and the tail ± nigrescent; calyx 3-4 mm long, pilosulous with silvery (rufescent), ascending hairs, the tube 1.7-2.1 mm long, a little recessed behind the banner, the ribs subfiliform, brown or nigrescent distally, the hyaline intervals plane and glandless, the ovate-triangular, mucronate or short-acuminate, nigrescent or livid, gland-spurred teeth (1.2) 1.4-2 mm long, the dorsal one sometimes longest, sometimes all nearly equal; petals 3 or 5, the banner and epistemonous pair or pairs concolorous, rose-purple, the latter perched at about the level of the calyx-sinuses, well below separation of most of the stamens, all eglandular; banner 2.7-3.7 mm long, the ovate-deltate, obtuse- or acute-angled, plane blade 1.4-2 mm long, 1.4-1.5 mm wide; wings (if present) and keel-petals not strongly differentiated in size or shape, 1.6-3.1 mm long, the oblanceolate blades 1.3-2.4 mm long, 0.6-1 mm wide, contracted at the scarcely oblique or auriculate base into a claw 0.3-0.8 mm long; androecium (4) 5, 6, or 7-merous, 3.3-4.3 mm long, 3 or 4 of the longer filaments usually free for only 0.5-0.8 mm and one (lateral to the androecial sheath) free almost to insertion of the epistemonous petals, the intervening filaments (if present) shorter, the connective gland-tipped, the anthers (of larger stamens) pale, ± 0.3 mm long; pod 2.5-3 mm long, described under the varieties.

Distribution and Ecology - This seldom collected, weedy but nevertheless exceptionally interesting annual Dalea is known from three widely separated localities in west-central Mexico. It was first met with by Pringle in 1887 on the headwaters of Rio Papigochic west of Ciudad Chihuahua (near lat. 28° 30' N), subsequently by Brother Arsene near Morelia de Michoacan (lat. 19° 40' N), and recently (1963, 1965) by Ripley & Barneby on the south edge of the Meseta Central, between Lagos de Moreno and Leon, near the Jalisco-Guanajuato boundary (lat. 21° 20'). At the last-named locality the plants grow in mud around the margins of ponds on the volcanic plateau, where they form dense colonies of stiffly upright stems, mixed and competing with a variety of small rushes, cyperaceae, and annual lobelias. The shallow root-system of each individual when pulled from the ground brings with it a pellet or ball of wet clay difficult to wash off, and as similar dried mud is seen on some specimens of the other collections mentioned, it seems likely that the habitat at Lagos is not accidental but typical for the species. No other Dalea tolerates water-logged soils.

Discussion

(Plate XLV)

The close relationship of D. confusa, as perceived by Rydberg, is to D. exigua. They are essentially similar in habit, have the same type of fine, weak, spiral hairs around the margins of the leaflets, and an equally degenerate androecium that varies between individual flowers from four to seven members, of which five are commonly more vigorous and bear larger anthers. The androecia differ, however, in one respect. In D. exigua the filaments, of whatever number, are all equally separated down almost to the insertion of the high-perching keel and form a short tassel typical of ser. Dalea. In D. confusa the petals are elevated much less far from the hypanthium rim, one lateral filament is separated down almost to the point of petal-insertion, while the rest are united high up beyond the petal- sockets. More easily observed differential characters of D. confusa are the denser, conelike spikes and the shape of the interfloral bracts, the body of which varies from oblanceolate to truncately flabeliate as opposed to deltate-ovate or somewhat rhombic in D. exigua. As already noted D. exigua is an obligate xerophyte which could not be expected to flourish in standing water, as D. confusa does at Lagos.

The five collections here referred to D. confusa are very similar in habit and vegetative characters but differ in fine detail of the perianth and the pod. The two gatherings from Chihuahua, made by Pringle probably at the same spot on the "pine plains" near Guerrero in 1887 and 1888, have five-petalled flowers; the blades of the keel are imbricated in vernation and adhere lightly by their faces. No really ripe pods were obtained, but the fully formed one is obliquely obovate in profile with a terminal style and a dilated, at least incipiently bicarinate prow. The plants from Jalisco and Michoacan are alike in having in many flowers only one pair of epistemonous petals, apparently representing the keel, the blades of which are free from the first. The dorsal suture of the ripe pod is so strongly developed in relation to the short ventral one that it becomes arched through much more than half a circle, displacing the style-base to a lateral position; and the suture itself, although a trifle thickened and prominent, is simple and not transversely dilated. When first discovered, the southern plant was interpreted as specifically distinct, and the two collections from Lagos were distributed under the name "Dalea hexandra" (nom. nud.). Pending the discovery of new stations and comparison of ample material at the same stages of growth I think it prudent to emphasize the likenesses rather than the differences and propose to treat the two types as geographic varieties.

Distribution

Michoacán Mexico North America| Jalisco Mexico North America| Guanajuato Mexico North America| Mexico North America|