Dalea exserta
Rupert C. Barneby
28. Dalea exserta (Rydberg) Gentry
(Plate XLVIII)
Erect annual herbs, commonly robust and coarse, up to (5) 6-10 (12) dm, exceptionally only 1.5 dm tall, glabrous to the inflorescence, the greenish, stramineous, or purple-tinged, ribbed, distally gland-verruculose stem simple at base, exceptionally monocephalous, usually branching upward from below or near the middle, the branches mostly terminating in a spike, the foliage green or subglaucescent, the leaflets smooth above, punctate beneath; stipular spurs up to 1 mm long, the blades triangular-subulate, subglandular, up to 1.5 mm long; intrapetiolular glands 2, spiculiform, deciduous; post-petiolular glands small but prominent; leaves somewhat dimorphic, the main cauline ones (drought-deciduous) 3-10 cm long, shortly petioled, with narrowly margined rachis and 9-18 pairs of oblong-elliptic to oblanceolate, obtuse and gland-mucronulate or emarginate leaflets 2-9 mm long, the uppermost leaves and leaflets smaller; peduncles rather stout, (1) 2.5-14 cm long; spikes moderately dense, oblong-ovoid becoming oblong-cylindroid, without petals or androecia (12) 13-16 mm diam, the villosulous or distally glabrous axis becoming (1.5) 2-8 cm long; bracts (3) 4-8 mm long, subdimorphic, the lowest commonly persistent, ovate- to broadly lance-caudate, the rest narrower but otherwise similar, early deciduous, all membranous-margined proximally, dorsally glandular, livid, and glabrous or nearly so, eciliate; pedicels 0-0.2 mm long; calyx at anthesis 4.8-7 mm long, narrowly turbinate, but somewhat accrescent and finally subtumid and oblong-ovoid, the tube (2.5) 2.7-3.8 mm long, glabrous or nearly so externally, deeply recessed behind the banner, the subfiliform ribs either livid or stramineous, the broad, glossily membranous intervals charged with 1-2 rows of ± 4 linear-elliptic, golden or orange blister-glands, the teeth triangular-aristate, (2) 2.3-3.8 mm long, usually about as long or slightly longer than the tube, rarely up to 0.6 (1) mm shorter, all plumose-ciliate with fine spiral rufescent hairs; petals all blue, or bicolored, the banner then opening white but early violascent, all or only the banner gland-tipped, the inner pairs inserted near or below middle of androecium, the keel-blades usually adherent by their narrowly overlapping exterior margins; banner 4.9-7.3 mm long, the claw 1.3-2.5 mm, the broadly lance-oblong to oblong-elliptic, obtuse or emarginate, almost erect blade 3-4.8 mm long, 2.2-3.3 mm wide; wings (2.8) 3.6-5 mm long, the claw 0.4-0.8 mm, the lanceolate or oblong, shortly auriculate blade (2) 3.4-5 mm long, 1-1.8 mm wide; keel 3.9-5 mm long, the claws 0.6-1.3 mm, the lunately elliptic or obliquely obovate blades 3-3.7 mm long, 1.1-1.6 mm wide; androecium 8-10-merous, (7.5) 8-11 mm long, the longer filaments purplish distally free for 0.9-1.6 mm, the connective gland-tipped, the pallid anthers 0.4-0.45 mm long; pod broadly obovoid- suborbicular, compressed, 2.2-2.8 mm long, slenderly keeled along the ventral and distal margins, the style-base lateral or latero-terminal, the papery-membranous valves charged with minute scattered glands, thinly pilosulous distally, finally dehiscent along the ventral suture; seed 1.6-1.8 (2) mm long; 2n = 14 (Mosquin).— Collections: 26 (iv).
Grassy openings in oak-woods, on pedregal in thorn forest, and in disturbed soils along highways and in fallow fields, mostly 1000-1800, perhaps rarely up to 2100 m, descending exceptionally to near 500 m, widely dispersed and locally common but the known stations highly discontinuous: w. slope of northern Sierra Madre Occidental in Chihuahua, adjoining Sonora, and just entering extreme s. Arizona (Santa Cruz County); Balsas Depression and Sierra Madre del Sur from w. Jalisco and Colima to Guerrero and Morelos; Atlantic slope of Mexican Plateau in Veracruz; centr. Oaxaca (Mixteca Alta); highlands of Chiapas through Guatemala (Alta Verapaz, Chimaltenango, and Guatemala) to Honduras (Morazan); Costa Rica (near Ocho- mogo and San Jose).— Flowering August to March. —Representative: UNITED STATES. Arizona: Goodding (Sycamore Canyon near Ruby) in 1939 (GH, NY). MEXICO. Chihuahua: Knobloch 5412 (F). Sonora: Gentry 518 (ARIZ, MICH); S. S. White 2705 (MICH). Jalisco: Gonzalez 186, p. p. (MICH). Colima: cf. type. Michoacan: Ripley & Barneby 14,794 (CAS, DAO, NY). Mexico: Hinton 2273 (F, K, MEXU, Z), 5048 (F, K, NY, Z). Morelos: Ripley & Barneby 14,561 (CAS, NY), 14,564 (CAS, DAO, NY). Guerrero: Hinton 9665 (F, NY). Veracruz: Purpus 2348 (F, NY, UC), 15,746 (UC). Oaxaca: Galeotti 3238 (P). Chiapas: Matuda 17,270 (F, MEXU). GUATEMALA. Alta Verapaz: Tiirckheim 2050 (NY). Guatemala: Standley 59,256 (F, NY). Chimaltenango: Standley 59,116, 64,307 (F). HONDURAS. Morazan: Standley 4023 (F). COSTA RICA. San Jose: Pittier & Tonduz 10,915 (BR, NY).
Dalea exserta (Rydb.) Gentry, Rio Mayo Pl. 138. 1942, based on Parosela exserta (protruded, of the long androecium) Rydb., N. Amer. Fl. 24: 73. 1924.— "Type collected at Colima, February 21 and 28, 1891, Edward Palmer 1312..." — Holotypus, US!
Dalea elata Mart. & Gal., Bull. Acad. Brux. 102: 41. 1843. — "Se trouve dans les savanes a hautes graminees de Zacuapan, pres Vera Cruz, de 2 a 3,000 pieds." — Holotypus, Galeotti 3264, BR (herb. Mart.)! isotypi, BR (herb. Galeott.), G, K, P, W! — Non D. elata H. & A., 1840.
Parosela lagopus sensu Rydb. in N. Amer. Fl. 24: 73. 1924 ("Lagopus"). — Non P. lagopus (Cav.) Cav., 1802, quae = D. leporina (Ait.) Bullock.
This coarse annual dalea is related both to D. leporina and D. urceolata; it might be visualized as a vigorous version of the former differing in its more massive spikes, externally glabrous calyx-tube, and long, far exserted androecium, from which the inner petals fall away at an early stage of anthesis. In its glabrous, incipiently tumid calyx which becomes more or less obviously ovoid or urceolate in fruit, D. exserta resembles D. urceolata, the latter’s short androecium being the most important, in the last analysis perhaps the only dependable differential character, and it is impossible to evade the question of whether there are two genuinely distinct species. Supposing, by way of hypothesis, that long-stamened populations have arisen more than once from an already polymorphic aggregate defined below as D. urceolata sens, lat., the problem of the highly discontinuous range of D. exserta would be solved. The populations found in the northern Sierra Madre would emerge as derived directly from var. urceolata native, at slightly greater elevations, in the same latitudes, and would be seen to bear the same relation to the latter as the more southern populations of D. exserta bear to D. urceolata var. tripetala. On the Balsas slope of the Neovolcanic Range in Mexico and Morelos D. urceolata var. tripetala is found principally in cool oak-pine forest at 2000- 2500 m, whereas D. exserta is encountered normally in a belt below it, mostly below the oak-line. However, near Cuernavaca var. tripetala descends the escarpment of Cuesta de Huitzilac onto pedregal within the range of D. exserta, and here the only substantial difference between them seems to be length of androecium, weakly supported by different norms of stature. In practice I have found no difficulty in dividing the material of D. urceolata and D. exserta into two groups and it seems prudent for the present to maintain these at the rank of species, remembering, however, that they are under suspicion and in need of further study.
It is unfortunate that Dalea elata Mart. & Gal., the first name proposed for D. exserta, is a later homonym, for the collection in which it is based is ample, and characteristic of the species as here defined. The holotype of Parosela exserta is much less satisfactory, consisting of a single individual plant collected in advanced fruit late in February at the low elevation of about 500 m near Colima. Rydberg treated tall, that is essentially normal D. exserta of this account under the name Parosela lagopus (a taxonomic synonym of D. leporina), setting off the new P. exserta (sens, str.) by its dwarf stature (± 1.5 dm) and glabrous raceme-axis. Close study of Palmer’s plant shows that the pilosulous pubescence found in most tall D. exserta is not altogether lacking; fine spreading hairs extend over the last centimeter of the peduncle and upward among the lower flowers, although absent distally. The same condition is found in a tall plant (Hinton 9665, NY) from Guerrero, which could not be separated on other grounds from Rydberg’s P. lagopus. The typus of D. exserta does remain, however, quite unusual in the context of this species for its small size. Furthermore I found in one flower, possibly not fully developed, that one pair of the inner petals was suppressed, a feature that I have not seen elsewhere in D. exserta, although it is normal in D. urceolata var. tripetala. Thus the typus of D. exserta combines the long androecium which I have emphasized as diagnostic with characters reminsicent of D. urceolata sens, lat., raising once again the problem stated in the preceding paragraph.
During the early stages of my study, when I had discovered Rydberg’s misidentification of Psoralea lagopus Cav. but had not taken the taxonomic step of uniting his Parosela lagopus with P. exserta, I used on several sheets of this species an unpublished epithet ("belgarum," commemorating Martens & Galeotti); some of these annotations I was later unable to rectify, the material having already passed out of my hands.
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:
