Dalea phleoides
Rupert C. Barneby
39. Dalea phleoides (Torrey & Gray) Shinners
(Plate LIV)
Perennial herbs of rapid growth, sometimes flowering the first season, with orange- red taproot and short caudex, (2.5) 3-7 dm tall, variably pubescent but at least the stems distally, or the leaf-rachis, or the upper face of leaflets (or some of them) ± densely pilosulous with weakly sinuous or incurved hairs up to 0.25-0.6 (0.7) mm long, the diffuse and ascending, ribbed, prominently livid-tuberculate stems either simple except for sterile branchlets in most axils or branched near middle, leafy in the lower 1/2-2/3, the foliage green or grayish-green, scarcely or strongly bicolored, the leaflets when dried either pale or verdigris above, livid-verruculose beneath; leaf- spurs 0.2-1.2 mm long; stipules narrowly subulate to linear-lanceolate or -caudate, castaneous, becoming dry and fragile, 1-4 mm long; intrapetiolular glands minute or 0, post-petiolular glands prominent, obtuse; leaves very shortly petioled, the primary cauline ones 2.5-5.5 (6.5) cm long, with narrowly margined, tuberculate rachis and 6- 20 ( 24) pairs of oblong, oblanceolate, or oblong-elliptic, obtuse or bluntly gland- mucronulate, or emarginate, flat or loosely folded leaflets 2.5-11 (14) mm long, the leaves of axillary fascicles or branchlets shorter, with fewer smaller leaflets of same type; peduncles (1) 2-20 (25) cm long; spikes very dense, the calyces contiguous, in outline at first long and narrow becoming sinuous in age, without petals 5.5—7.5 (8.5)mm diameter, the densely pilosulous to glabrous axis (1.5) 2.5-9 (13) cm long; bracts subdimorphic, the lowest firm and persistent, the interfloral ones deciduous but held fast between the calyces and falling with them, these narrowly lance-acuminate or -caudate, 2.5-4.5 mm long, subscarious toward base, livid-castaneous distally, dorsally pilosulous and ± glandular, the slender tips either as long as the buds or well exserted before anthesis; calyx very obliquely compressed-ovoid, spreading sub- horizontally or declined from the axis of the spike, 2.5-3.8 mm long, the tube measured to a lateral sinus 1.7-2.5 (2.8) mm long, deeply recessed behind banner, either glabrous or pilosulous externally (the hairs up to 0.2-0.45 mm long), the subfiliform ribs castaneous, hardly prominent, the rather firm, often castaneous-flecked intervals very unequal, the dorsal and lateral ones narrow, charged above middle with 1-2 glands, the broad ventral ones with 3-5 (7) scattered glands, the teeth all crowded toward the abaxial side of the orifice, up to 0.5-1.2 mm long, of nearly equal length but dissimilar in shape, the 3 abaxial ones subulate, the adaxial pair broadly deltate- ovate, all usually glabrous externally, within always pilosulous; petals white, glandless, the epistemonous ones perched at the sinuses between filaments, the abaxial pair slightly higher than the lateral; banner 5.3-6.8 mm long, the claw (2.5) 3-3.8 mm, the bluntly deltate, deeply cordate, often apically emarginate and hooded blade 2.8 3.5 (4) mm long, 2.6-3.6 (5.2) mm wide; epistemonous petals all alike or the inner pair a trifle larger, 4.1-5.9 mm long, the linear-oblong or -oblanceolate, ribbon-like blades 0.5-0.9 mm wide, tapering at base into a claw 1.1-2 mm long; androecium 5.2-7.4 mm long, the column (1.8) 2-3.2 mm long, the free filaments up to 3-4.3 (4.8) mm long, the connective gland-tipped, the pale yellow or orange-yellow anthers 0.6-0.9 mm long; pod obliquely obovate in profile, ± 2.5-2.9 mm long, the style- base terminal, the prow slenderly carinate, the valves papery, scarcely transparent at base, pilosulous and sometimes gland-sprinkled distally.
A white prairie-clover instantly recognized by its many leaflets, firm narrow spikes of crowded, strongly asymmetric calyces, and ribbon-like epistemonous petals. The calyces stand out horizontally from the axis of the spike and present to exterior view, in place of the five-lobed orifice usual in Dalea, a vertical ciliate slit formed by the margins of the inner calyx-teeth, the points of these and of the abaxial teeth being all crowded together at the nether extremity. The species is morphologically very distinct and was found by Wemple (1970, p. 8) to be isolated by genetic incompatibility from other members of the group Candidi.
My concept of D. phleoides is equivalent to Petalostemon group Phleoides of Wemple (1970, pp. 54-57, map 8) who, quoting an unpublished study by W. S. Jackson, recognized within it two species, P. phleoides and P. microphyllum. Both were known to be highly variable internally, seeming to consist of a mosaic of races differing among themselves in pubescence, number or size of glands and of leaflets, and size of calyx. Most of the phenotypic variables are weakly correlated if at all, but relatively few and large leaflets seem to go hand in hand with a calyx externally glabrous and grossly glandular; these removed as P. phleoides, the residue, with calyx sometimes hairy all over, sometimes only near the base, combined with smaller and more numerous leaflets but still heterogeneous in other respects, is defined as P. microphyllum. Sorted in this way, the two types are found to have substantially different but at same time widely overlapping ranges of dispersal and where they overlap a common habitat. The forms with fewer larger leaflets, in which a sort of leafy impulse is often expressed upwardly on the peduncle in the shape of enlarged bracteiform stipules (or stipuliform bracts) and elongated true interfloral bracts, is confined to the sandy woodlands of the Gulf Coastal Plain, whereas P. microphyllum, pubescent like P. phleoides where they grow together, extends northward and far inland to the Red River and north foothills of Edwards Plateau, where the foliage becomes often hairless or almost so. Wemple and Jackson assume that the individual populations of either entity have little contact, and explain the internal variability of both in terms of isolation of breeding-lines. The same circumstances would enable two related species to maintain themselves in pure form even though they are adapted to the same environment and are in practice sympatric. On the other hand a shift of emphasis from the small differences, acknowledged variable in themselves, to the multiple and constant similarities, justify a return to the original varietal status accorded to P. microphyllum on its discovery. The sorts of phenotypic variation encountered in Dalea phleoides sens. lat. are encountered repeatedly in Amorpheae: the foliose tendency, exhibited also, in the same territory, by the purple prairie-clover D. compacta; and that often misleading and inscrutable variability in pubescence to which I have given prominent attention throughout this account.
References: [Article] 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.Multimedia:
