Dalea

Title

Dalea

Authors

Rupert C. Barneby

Scientific Name

Dalea L.

Description

IV. DALEA Lucanus

Herbs (perennial, monocarpic) and shrubs, some attaining treelet stature, the stems, leaves, and usually the flowers containing secretory vesicles (herein called glands) charged with aromatic oils, these taking the exterior form of lens-like, hemispherical, grainlike, or prickle-shaped blisters, the plant body, sometimes only the orifice of the calyces, ± pubescent with spiral, when dry nearly always rufescent hairs; stipules herbaceous or subglandular; leaves imparipinnate (D. similis paripinnate) or rarely trifoliolate, the terminal leaflet either elevated above the last pair or sessile and forming with the last pair a palmate trefoil, the leaf-rachis narrowly green-margined and commonly bearing at insertion of the petiolulate or sessile leaflets a pair of glands in front and a pair behind, these termed intra- and post-petiolular, the intrapetiolular pair sometimes confluent into a single gland; inflorescence a spike or a raceme, moderately or quite loose when racemose, loose to very dense when spicate, when extremely dense and hard termed herein conelike; calyx subtended by a deciduous or persistent bract and by 2 usually minute, sometimes spiculiform, sometimes obsolete, glandiform braceoles, these situated either on the rachis of spike or on the individual pedicel; tube of calyx 10 (D. galbina 20)-ribbed, 5 produced into apex of teeth and usually excurrent as a gland-tipped mucro, the arms of the 5 alternate ones, Y-forked below the sinuses between the teeth, produced into the teeth and normally anastomosing with the adjacent rib to form a gallery of closed panels, these often differentiated in texture, membranous or hyaline and charged with 1-several ranks of glands arranged in patterns characteristic for the species, but the panels sometimes glandless, sometimes firm; teeth of calyx varying from low-deltate to ovate, triangular, subulate, or elongately caudate-aristate, their margins often charged with 1 or more glandiform spurs; petals all white or of various colors (blue, purple, pink, ochroleucous, yellow, if yellow often fading orange, brown, black), the banner either concolorous with the rest or very often opening pallid (white, yellowish) or with pallid eye-spot and early rubescent, contrasting with ± anothocyanic wings and keel; banner either longer or (commonly) shorter than the detached keel, its blade either plane or variously hooded and at base thickened or there recessed into an obconic pit (comet); wings and keel, herein termed collectively epistemonous petals, perched on and (except in few spp. of sect. Theodora) disjointing from sockets on the androecial column, the keel-blades either free in vernation, or narrowly imbricate and adherent by their overlapping faces, or valvately coherent into a conventional navicular keel, the wings, exceptionally also the keel, in some advanced annual spp. degenerate or 0; androecium usually 10-, sometimes 9-, in sect. Kuhnistera exactly 5-, in several spp. of subgen. Dalea indefinitely 5-10- but functionally 5-merous, the sheath cleft to various depths into a tassel, sometimes down to the petal-sockets; anther-connective often gland-tipped; pollen-grains tricolpate, operculate, commonly prolate, rarely spheroidal, in some spp. of sect. Theodora "amphisbaenoid" (narrowly oblong and enlarged at either pole); pod varying in outline from obliquely obovate to deltate, the ventral suture straight, slightly concave, or slightly convex, grooved on back and provided behind the attachment of the ovarian funicles with a small pore, the ventral suture always longer, curved or abruptly bent through more than half a circle, filiform or sometimes dilated distally; style filiform, or somewhat dilated distally, the stigma (maturing with or after the pollen) minute or rarely subcapitate; ovules 2, collateral, only 1 fertile; seed moderately compressed, notched at the punctiform hilum, the coat smooth; x = 7, rarely (sect. Theodora, perhaps subgen. Psoropteris) 8.— Spp. 161 (described; certainly somewhat more), dispersed over much of temperate, prairie, desert, and both arid- tropical and montane-tropical North America, most abundant and diverse in Mexico, with secondary focus of speciation at moderate and high elevations along the Andes of South America from Colombia to n.-w. Argentina and n. Chile, a few circum-Caribbean, 1 on Islas Galapagos, 2 adventive in extra-Andean South America n. of the Equator, 1 fully naturalized in Islas Filipinas, in North America absent from the w. slope of the Sierra-Cascade axis and from the Atlantic slope of the Appalachians n.- ward from North Carolina, a few n. over the plains into prairies of s. Canada. Xerophytes (with trifling exceptions), avoiding tropical forest, abundant and highly developed in the oak-pine woodlands of intertropical Mexico and Central America.

Dalea Lucanus⁷, Linnaei Opera Varia (Soulsby Cat. no. 9) 244. 1758, nom. conserv. (Dandy, Regn. Veg. 51: 15, 45. 1967); non Dalea Mill., 1754. — Generitypus, Dalea L., Hort. Cliff, t. 22. 1738 = Dalea cliffortiana Willd.

My concept of Dalea, as defined in the foregoing keys to genera of Amorpheae and to the four genera described herein in monographic detail, can be expressed by the equation: Dalea = (Parosela sensu Rydb., — Marina sensu Barneby) + Thornbera Rydb. + (Petalostemum Michx. Kuhnistera Lamk.). In number of species it maintains almost the same compass as Parosela sensu Rydb. (1919-20; 1928), the loss of Marina being compensated by the accessions of Thornbera, Petalostemum, the Andean daleas, and species subsequently described. The genus is no longer characterized by insertion of the epistemonous petals at one particular level (or levels) between the hypanthium and the separation point of the filaments or by the number of functional stamens, but by attributes, seemingly more fundamental, of ovule- and chromosome-number. The generic character is drawn so as to embrace all Amorpheae furnished with epistemonous petals combined with two collateral ovules and a basic chromosome complement of seven or (rarely) eight; thereby excluding Marina (uniovulate) and Psorothamnus (with sessile petals), both of which have, so far as known, a basic chromosome number of ten.

The advantage of this comprehensive concept is its impregnable boundary: no species is doubtfully included or doubtfully excluded from the fold. The disadvantages are two: an internal heterogeneity, almost inevitable in genera of comparable size, but less extreme than found in Parosela sensu Rydberg; and the disappearance into synonymy of Petalostemum:, long familiar and therefore dear to botanists in North America, especially in United States. The reduction of Petalostemum and, as a corollary, that of Kuhnistera, is nothing new, however. These genera were combined with Dalea long ago by Jussieu, Ventenat, and Sprengel, and in modern times by Shinners (1949), who provided most of the ensuing new names or combinations. The reduction of Thornbera will be less keenly felt; the species are largely Mexican and therefore less well known, and the genus has been taken up, since its publication, by only one author of note (Wiggins, 1940). Rydberg included in his concept of Thornbera (1920) the generitype of Dalea as currently received (nom. conserv.), a fact that has no bearing on the taxonomic validity of Thornbera as a genus, but pretty well ensures its status as a synonym.

⁷The anonymous citizen of Lucca, editor of Opera Varia, who accidentally provided technical validation of Dalea "Linn.", a genus explicitly, repeatedly, and in all his major works from 1753 onward rejected by Linnaeus himself. The point is discussed by Barneby (1965) and by Dandy (Regn. Veg. 51: 15, 45. 1967), who has pointed out that there is nothing in the International Rules to disqualify Opera Varia as a medium of valid publication. However the Code requires that an author accept his own taxonomic decisions unequivocally at the moment of publication. A Dalea Lucanus, nom. conserv. is acceptable, but a Dalea Linn, is possible only if the starting-date for the Phanerogams can be put back to Hortus Cliffortianus, 1737. In any other circumstances "Dalea Linn." incorporates a falsehood.