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(Last Modified On 9/26/2013)
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(Last Modified On 9/26/2013)
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Reference
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Blake, S. F. 1924. New American meibomias. Bot. Gaz. 78: 271-288. Ohashi, H. 1973. The Asiatic species of Desmodium and its allied genera (Le- guminosae). Ginkgoana 1: 1-318; pls. 1-76. Schindler, A. K. 1928. Die Desmodiinen in der botanischen Literatur nach Linne. Repert. Spec. Nov. Regni Veg. Beih. 49: 1-371. Schubert, B. G. 1940. Desmodium: preliminary studies I. Contr. Gray Herb. 129: 3-31. Schubert, B. G. 1941. Desmodium: preliminary studies IL. Contr. Gray Herb. 135: 78- 115; pls. 1-3. Schubert, B. G. 1963. Desmodium: preliminary studies IV. J. Arnold Arbor. 44: 284- 297.
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Key
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a. Leaves regularly unifoliolate, leaflets linear lanceolate; sutures of the whole loment remain- ing more or less intact after the walls of the articles fall away ...... 3. D. angustifolium aa. Leaves regularly trifoliolate, leaflets not linear lanceolate; each article of the loment de- taching with its sutures intact or the upper suture alone pulling away (starting at the prox- imal end of the loment), or rarely the articles partially separating, then dehiscing along the lower suture. b. Articles of loment with dorsal (upper) suture straight to deeply concave, i.e., narrowly or broadly notched or indented. c. Articles of the loment almost orbicular or saccate in outline, essentially flat, notched on the dorsal suture, not filled by the seed. d. Articles small, almost as broad (high) as long, 10-12 mm broad (includ- ing notch), 12-14 mm long, notch on dorsal suture narrowly V-shaped, article + beaked at the termini of the dorsal suture; stipe + equal to pedicel in length, essentially glabrous ...... 11. D infractum dd. Articles of the loment much larger, usually 2 cm or more long and high; notch on dorsal suture narrow to broad; articles beaked or not; stipe equal to or exceeded by the pedicel, puberulent to pubescent or glabrate. e. Articles with flattened shoulders or else beaked when fully mature; leaflets + tomentose on abaxial surface; stipe of loment pubescent. f. Articles with flattened shoulders when mature; pedicel about equal to the stipe in length ...... 13. D. macrodesmum ff. Articles with shoulders only partially, if at all, flattened, be- coming beaked when fully mature; pedicel usually exceeding stipe ...... 18. D. rhynchodesmum ee. Articles without flattened shoulders and not becoming beaked at maturity, the notch forming a sharply acute or obtuse angle; leaf- lets not tomentose on abaxial surface; pedicel exceeding the glabrate stipe in length ...... 19. D. saccatum cc. Articles of the loment smaller and not saccate or orbicular in outline, essentially filled by the seed when mature; the dorsal suture straight or only slightly con- cave or invaginated at the center. g. Flowers borne in pairs; each pair subtended by 1 large primary bract; each pedicel usually subtended by a smaller secondary bract, or secondary bract lacking. h. Each pair of pedicels subtended by a primary bract; each pedicel usually subtended by a smaller secondary bract. i. Stems with inconspicuous pubescence of short hooked trichomes; leaflets short pilose on abaxial surface. j. Leaflets rhombic, rhombic ovate, or rhombic orbicular, obtuse or rounded at apex; stipe of loment 3-4.6 mm long ...... 4b. D. axillare var. axillare jj. Leaflets ovate, rather abruptly short acuminate; stipe of loment 4.6-8 mm long ...... 4c. D. axillare var. stoloniferum ii. Stems with long dense pubescence of straight trichomes; leaflets ovate or elliptic ovate, long pilose abaxially, acute to gradually (usually long-) acuminate ...... 4a. D. axillare var. acutifolium hh. Each pair of pedicels subtended by a primary bract only; secondary bracts lacking. k. Primary bracts early deciduous, inflorescence lax; calyx puberulent and slightly short pilose along central tooth of lower lobe. 1. Leaflets (terminal) to 2.3 cm long and 1.5 cm wide; articles of the loment to 5.5 mm long ...... 1. D. adscendens 11. Leaflets (terminal) to 0.6 cm long and 0.7 cm wide; articles of the loment to 4.5 mm long ...... 23. D. triflorum kk. Primary bracts persistent, inflorescence dense; calyx long silky pilose and ciliate ...... 5. D. barbatum gg. Flowers borne singly (rarely in D. incanum more than one in a fascicle), each pedicel subtended by 1- large primary and 2 smaller secondary bracts. m. Loments multiarticulate, dorsal suture straight; isthmi broad or narrow; margins of leaflets not undulate. n. Isthmi (area between the articles) nearly equaling length of article, loments to 7-articulate; leaflets thick, veins prominent ......10. D. incanum nn. Isthmi (area between the articles) narrow, loments to 4-articulate; leaflets thin, veins not prominent ...... 2. D. affine mm. Loments 2-3-articulate, dorsal suture curved or invaginated; isthmi very narrow; margins of leaflets undulate ...... 24. D. wydlerianum bb. Articles with dorsal suture straight to curved, or obtusely to acutely angulate. o. Pedicels borne in fascicles of 2-several, each fascicle subtended by a narrowly ovate, greenish to stramineous primary bract; each pedicel further subtended by a similar slenderer secondary bract; young inflorescences with fascicles early distinct. p. Isthmi between articles central. q. Plants prostrate; articles slenderly elliptic, sutures scarcely constricted at isthmi ...... 20. D. scorpiurus qq. Plants erect, mostly tall and usually becoming shrubby; articles chiefly rhombic in outline (excepting occasionally the terminal), sutures markedly constricted. r. Terminal article of each loment regularly much dilated, reniform to elliptic ...... 9. D. glabrum rr. Terminal article of each loment equaling the others in size and shape. s. Leaflets thick and with prominent reticulate venation. t. Pedicels stiff, ascending to spreading at maturity, borne in pairs ca. 1 cm apart, 1-1.6 cm long; articles of the loment 3-3.5 mm long, 2.6-3.5 mm wide ...... 22. D. tortuosum tt. Pedicels more slender, ascending, borne in pairs less than 1 cm apart, 1 cm (or less) long; articles of the loment smaller, 1.5-2.5 mm long, 1.5-2 mm wide. u. Leaves regularly trifoliolate, abaxial surface rough; pedicels 6-10 mm long; at least the terminal (sometimes 3) article glabrous ...... 8. D. distortum uu. Leaves regularly unifoliolate, abaxial surface velvety tomentose; pedicels 2.5-3 mm long; all articles of the loment with some straight pubescence ...... 16. D. perrottetii ss. Leaflets thinner, not prominently reticulate. v. Pedicels to about 1.2 cm long, straight, stout; bracts deciduous; articles appearing twisted but not coiled 17b. D. procumbens var. procumbens vv. Pedicels longer, usually 1.2-2 cm long, flexuous, filiform; bracts persistent; articles appearing to be tightly coiled ...... 17a. D. procumbens var. longipes pp. Isthmi between articles eccentric ...... 7. D. campyloclados oo. Pedicels borne in pairs, each pair subtended by a broadly ovate, stramineous to olivaceous primary bract; each pedicel usually further subtended by a smaller, sometimes differently shaped and much thinner and paler, i.e., depauperate, secondary bract; young inflorescences with bracts densely imbricate. w. Isthmi between articles central ...... 14. D. maxonii ww. Isthmi between articles eccentric. x. Pedicels short (2.5-6 mm long), reflexed or erect at maturity, leaflets sometimes lustrous above. y. Stems and leaflets sericeous tomentose; pedicels strongly reflexed in fruit ...... 21. D. sericophyllum yy. Stems pilose, leaflets lustrous above; pedicels erect at maturity ...... 6. D. cajanifolium xx. Pedicels longer (mostly 1-2 cm long) or, if not longer, then pedicels not sharply reflexed in fruit and leaflets not lustrous above. z. Scandent to erect plants with stout trisulcate stems ...... 12. D. intortum zz. Prostrate or decumbent plants with slender terete stems ...... 15. D. molliculum
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Genus
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DESMODIUM Desv.
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Contributor
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B. G. Schubert
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PlaceOfPublication
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Jour. Bot. ser. 2. 1: 122. P1. V, Fig. XV. 1813
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Note
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nom. cons. TYPE: D. scorpiurus (Sw.) Desv. = Hedysarum scorpiurus Sw., typ. cons.
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Synonym
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Meibomia Heister ex Fabr., Enum. 168. 1759. LECTOTYPE: Hedysarum canadense L. Perrottetia DC., Ann. Sci. Nat. 4: 95. 1825, non H.B.K. Nov. Gen. Sp. P1. 7: 57 (folio ed.); 7: 73 (quarto ed.). t. 622. 1824 [Celastraceae]. See DC. Mem. Legum. 312. 1826.
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Description
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Herbs, subshrubs, or shrubs, prostrate or scrambling to erect. Leaves 1-3 (or rarely-5)-foliolate, petiolate, stipulate; leaflets petiolulate and stipellate. In- florescences axillary or terminal, racemose or racemose paniculate, or extremely dense and capitate; primary bracts striate and ciliate, each subtending 1 (pedi- cellate) flower, or a fascicle of 2 to several flowers; secondary bracts often pres- ent, similar to the primary bracts or depauperate, each subtending a single flower; bracteoles rarely if ever present in American species. Flowers pedicellate, pap- ilionaceous, calyx 2-lobed, the upper lobe almost entire to bifid, the lower 3- toothed with the central tooth longer than the laterals, or the calyx almost equally 5-lobed; corolla exceeding the calyx, the standard slightly clawed, wings some- what so, wings often attached to keel petals by a small appendage, keel petals long clawed, partially fused above; vexillary stamen free or partially fused; an- thers uniform; ovary sessile or stipitate, ovules 2-many, the style slender, the stigma terminal. Fruit lomentaceous, i.e., transversely septate and forming (1-)2- many articles, usually stipitate, indehiscent, or tardily dehiscent, or in 1 species in Panama the walls between the sutures falling away leaving the sutures as a frame; articles variously shaped from nearly linear to almost saccate or circular and notched at the apex, sometimes folded on each other in accordion fashion (at least when young), the surfaces glabrous to densely pubescent with straight tapering or hooked trichomes, or these only on sutures, the articles 1-seeded. Seeds oblong or subquadrate to reniform.
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Habit
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Herbs, subshrubs, or shrubs
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Note
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A genus of some 300 or more species of tropical and temperate areas of the world excepting New Zealand, Europe, and the United States west of the Rocky Mountains. Standley (1946) records one species in cultivation in southern Cali- fornia as an ornamental. The greatest center of diversity is in eastern Asia; centers of considerable magnitude occur also in Brazil and Mexico. There is a large group of ruderal species, some of which have become pan- tropical weeds, and another group of species, growing only in woodlands and forests, which are less abundant and have more precise and restricted distribu- tion. Representatives of both groups occur in the flora of Panama. The fruits of many species are covered with hooked hairs which become attached to passing animals or to trouser legs very easily. This accounts for much of the distribution of weedier species. It is also the reason for the rather wide- spread common name "pega pega" applied to many species. The reason for Hutchinson's placement of the genus Desmodium under that branch of his key having "Fruits without hooked hairs" is puzzling. The genus Desmodium is the largest member of the tribe Desmodieae, even if considered in the narrowest sense and with many subgeneric taxa raised to generic status. It is treated broadly here with the "satellite" genera maintained in infrageneric categories. Specimens of one collection, Tyson 6339 from Chiriqui Province, have come to me from MO and FSU. The Missouri sheet was annotated as Desmodium caripense "vel sp. aff." The Tyson material differs from D. caripense, however, in shape and pubescence of the leaflets, those of D. caripense being ovate atten- uate in outline, and glabrous or glabrescent on the abaxial surface; in having longer, persistent, more obviously clasping stipules; and in number of articles per loment. It is similar to D. venustum Steudel of Mexico which, however, has long bracts (0.9-1.5 cm) that are gradually acuminate; it seems also to bear some relationship to D. alamanii DC. which differs in its densely pyramidal, much shorter inflorescences, slenderer primary bracts, shorter pedicels, and smaller glabrescent articles of the loment. From D. ghiesbreghtii Hemsley the Tyson material differs in its much longer persistent stipules, longer pedicels (14 mm vs. 4 mm, in fruit in D. ghiesbreghtii), and longer and broader loment articles. Ad- ditional material, especially in flower, will help to determine whether Tyson 6339 is an undescribed species and if its relationship is with those species noted here as well as with D. maxonii and its other relatives treated in an earlier paper (Schubert, 1941). The label on the Tyson collection reads: Chiriqui, canyon of waterfall 5 mi NE of El Volcain, 6500 ft.
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