SYNOPSIS OF LEUCOSYRIS, INCLUDING SYNONYMOUS ARIDA (COMPO SITAE: ASTEREAE) John F. Pruski Missouri Botanical Garden P.O. Box 299 St. Louis, Missouri 63166 Ronald L. Hartman Department of Botany University of Wyoming Laramie, Wyoming 82070 ABSTRACT The genus Leucosyris is revived, reviewed, and expanded to include nine species from the southwestern USA and northern Mexico. Arida is reduced to synonym}' of Leucosyris, and eight new combinations in Leucosyris are proposed. KEY WORDS: Arida, Asteraceae, Astereae, Compos itae, Leucosyris, Machaer anther a, Psilactis. A generic review of the mostly radiate-capituhte Machaer anther a Nees alliance (Morgan and Hartman 2003) recognized the aptly named Arida (R.L. Hartm.) D.R. Morgan & R.L. Hartm. (Compositae: Astereae: Machaerantherinae), but did not emphasize that included within Arida was the type (Linosyris carnosa A. Gray) of Leucosyris Greene (5 Aug 1 897). Here, we emend that work by reducing Arida to taxonomic synonymy of a reinstated Leucosyris, a name which has priority over Arida by more than a century. We also provide a synopsis of Leucosyris and its nine species, abbreviated synonymy and typology, and eight new combinations in Leucosyris. As an. aside, the illegitimate later homonym Linosyris Cass. (1825; non Linosyris Ludw., 1757, Santalaceae) is unavailable nomenclaturally and not congeneric taxonomically with our plants, but rather the Cassini name is typified by European material. It appears that the available name Leucosyris has often stood in the shadows, this perhaps a by-product of its type being described in Linosyris. Machaer anther a was described by Nees (1832) and accepted by Candolle (1836) and Gray (1852, 1853). Bentham and Hooker (1873) reduced Machaer anther a to Aster sect. Machaer anther a (Nees) Benth. & Hook, f, in which Gray (1884) recognized seven species. Machaer anther a was reinstated as a genus by Greene (1896), and Greene (1899) recognized about two dozen species, these mostly taprooted and blue-rayed.. Shinners (1950) expanded Machaer anther a to include a few yellow-rayed species, but these yellow-rayed species were excluded from Machaer anther a by Cronquist and Keck (1957). Hartman (1976, 1990) reviewed Machaer anther a and recognized 36-38 species spread unequally among two subgenera and eight sections. Most of the species recognized by Hartman (1976, 1990) as Machaer anther a (i.e., M. subg. Machaer anther a) were characterized by having taproots, bristled- or pinnatilobed leaves, ray florets with blue to less commonly white corollas, and base chromosome numbers of x = 4, 5, or 6, but the handful of species placed in M. subg. Sideranthus were yellow-rayed. Hartman (1976, 1990) recognized only two species ofM. sect. Machaer anther a, and the larger sections he recognized included sect. Blepharodon (with nine species) and the newly described blue-rayed sect. Arida (with eight species). At about the same time mat Greene (1896, 1899) resurrected Machaeranthera, he (Greene 1897a) described Leucosyris to accommodate a single discoid species. Leucosyris (or its type, Linosyris carnosa, albeit often as Aster intricatus) was subsequently recognized as including only Pruski and Hartman: Synopsis of Leucosyris 2 Leucosyris (Chloracantha) spinosa (Benth.) Greene by Wooton and Standley (1915), but treated within Aster by Hall (1907), Blake (1925, 1942), Jepson (1925), Tidestrom and'Kittell (1941), Munz and Keck (1959), Ferris (1960), Shreve and Wiggins (1964), Munz (1974), Jones (1980), and Semple and Brouillet (1980). More recently, Leucosyris was recognized as monotypic by Sundberg (1986), with two species by Gandhi and Thomas (1989), L. carnosa was placed within Machaeranthera by Hartman (1976, 1990), Nesom (1989), Nesom et al. (1991), Keil et al. (1993), and Felger (2000), but Leucosyris was reinstated by Cronquist (1994), again as monotypic. Morgan and Hartman (2003) summarized the recent dismantling of Machaeranthera, which they recognized in the narrow sense as containing only the two species of M. sect. Machaeranthera sensu Hartman (1976, 1990). Most former Machaeranthera species were heated by Morgan (1993) and Morgan and Hartman (2003) variously among resurrected Dieteria Nutt. (x = 4: 3 spp.), Psilactis A Gray (x = 3, 4, 9; 6 spp.), Xanthisma DC. (x = 2, 3, 4, 8; 17 spp., including yellow-rayed subg. Sideranthus as well as sect. Blepharodon), and the newly elevated Arida. Nesom and Robinson (2007) placed most of these genera into subtribe Machaerantherinae, but by non-bristle tipped leaf teeth and chromosome number they treated Psilactis as Symphyotrichinae. We recognize Leucosyris (x = 5; 9 spp.) in the same sense that Morgan and Hartman (2003). Hartman and Bogler (2006), and Nesom and Robinson (2007) circumscribed Arida, despite the discrepancies between cpDNA and nrDNA studies (nrDNA studies place L. parviflora and L. riparia in different subclades), which Morgan and Hartman (2003) attributed to reticulate evolution. LEUCOSYRIS Greene, Fl. Francisc. 384. (5 Aug) 1897. TYPE: Linosyris carnosa A. Gray (= Leucosyris carnosa (A Gray) Greene). Machaeranthera sect. Arida R.L. Hartm., Phytologia 68: 446. 1990. Arida (RL. Hartm.) D.R. Morgan & R.L. Hartm., Sida 20: 1410. 2003. TYPE: Machaeranthera arida B.L. Turner & D.B. Home (= Leucosyris arida (B.L. Turner & D.B. Home) Pruski & R.L. Hartm.). Annual or biennial herbs to short-lived perennial weak subshrubs 10-80(-150) cm tall, usually taprooted, infrequently rhizomatous; stems usually ascending to erect; herbage (when glandular) usually with short stipitate-glands. Leaves alternate, the basal (often withered) often petiolate, the cauline sessile and commonly clasping, entire to bipinnatifid, lobes or teeth often hyaline bristle-tipped, never sharply bristle-tipped, surfaces glabrous or pubescent, sometimes stipitate-glandular. Capitulescence corymbiform to open-c) T mose, capitula monocephalous on branchlets; peduncles often with bracteoles loosely grading into phyllaries. Capitula radiate (heterochromous) or infrequently discoid; involucre turbinate to hemispherical; phyllaries mostly 40+, imbricate, graduated, 3-8-seriate, persistent, linear-lanceolate to narrowly oblong, stiff, base usually indurate and stramineous, apex often with dark green to purplish mid-zone or more commonly patch, abaxial surface glabrous to pubescent or glandular; receptacle epaleate, convex, somewhat alveolate. Ray florets (0 or)8-50+, pistillate, 1-seriate; corolla limb usually pale blue to dark blue (infrequently white), usually drying brownish-yellow, often coiling when old or pressed. Disk florets (5-)10-100+, bisexual; corolla gradually narrow-funnelform, 5-iobed, yellow, lobes triangular; anthers pale, appendage lanceolate; style branch appendage narrowly triangular, papillose. Cypselae weakly dimorphic, those of the rays subtriquetrous, those of the rays disks subcompressed, narrowly oblong, stramineous to pale brownish, faces 7-13-striatulate, sericeous, distal trichomes of disk cypselae often reaching to pappus bristle base; pappus of many stramineous filiform capillary scabrid bristles, bristles contiguous basally, indistinctly ca. 2-seriate, disks always pappose, rays pappose or epappose. x = 5. Leucosyris as treated here in the expanded sense basically may be thought of as a segregate of Machaeranthera- Indeed, revisionary treatments of three of its species by Turner and Home (1964) as sect. Psilactis and of a fourth (L. blepharophylla as M. gyps itherma) by Nesom et al. (1990) as Pruski and Hartman: Synopsis of Leucosyris 3 sect. Arida were each under the umbrella of Machaeranthera. The base chromosome number of Leucosyris is x = 5 and its species mostly have been reported under names in Machaeranthera (e.g., Arnold and Jackson 1978 and Turner et al. 1975). However, Machaeranthera in the strict sense differs from Leucosyris by a base chromosome number of x = 4 and by sharply bristle-tipped leaf lobes. Genera in which the basionyms of our nine recognized species were described include Arida (1 sp.), Aster (2 spp.), Linosyris (1 sp.), Machaeranthera (3 spp.), and Psilactis (2 spp.). Attempted lectotypifications of a few names based on sheets taken here as Asa Gray holotypes have been hazarded elsewhere, but none affect any species circumscriptions. The nine species of Leucosyris are mostly summer- or late-blooming and occur from sea-level to about 2200 meters elevation in salt flats, scrub lands, dunes, deserts, sulphur pools, limestone hills, cliff faces, or less commonly along streamsides or in flood plains of the southwestern USA and northern Mexico, with only L. riparia (Kunth) Pruski & R.L. Hartm occurring as far south as Durango and Zacatecas (and perhaps Guanajuato), Mexico, near the Tropic of Cancer. Etymology: The name Leucosyris Greene is derived from Linosyris Cass., which is typified by Chrysocoma linosyris L. (now Crinitaria linosyris (L.) Less.). The Linnaean epithet alludes to the resemblance of the linear-leaved composite to the subsucculent-leaved European-African Santalaceae genus Osyris L. Indeed, the protologue of C. linosyris cited the pre-Linnaean 160 1 Clusius usage of Osyris austriaca as an original element of the composite. Jackson (1987) and Hyam and Pankhurst (1995) noted that Osyris (used by Bauhin, Dioscorides, Pliny, van Royen, etc.) is derived from the Greek ozos, in reference to the dense branching of the Santalaceae genus. The name Leucosyris, derived from ozos, is thus not a homonym of Leucoseris Nutt, wherein the suffix seris (Brown 1956) is a Latin word for "a kind of endive. " KEY TO SPECIES OF LEUCOSYRIS 1. Capituia discoid (sparsely leafy to nearly leafless wiry-reedy or rounded and tumbleweed-like subshrubby herbs) Leucosyris carnosa 1. Capituia radiate. 2. Ray cypselae pappose. 3. Cauline leaves entire, subsucculent 4. Caespitose perennials; leaf margins 8-20-spinulose-ciliate, spinules 0.4-1.5 mm long; involucres 5-8 mm diam Leucosyris blepharophylla 4. Annual leaf-stemmed herbs; leaf margins sometimes soft-ciliate; involucres 10-16 mm diam Leucosyris riparia 3. Cauline leaves (mostly) pinnatilobed to 2-pinnatifid, chartaceous. 5. Receptacles 2-7 mm diam.; phyllary apices mostly appressed Leucosyris parviflora (in part) 5. Receptacles 8-11 mm diam.; phyllary apices spreading to reflexed Leucosyris turned Pruski and Hartman: Synopsis of Leucosyris 4 7. Herbage densely stipitate-glandubr (at least some cauline leaves pinnatilobed). 8. Herbage heterotrichous; involucres 3,5-6 x 5-9 mm; disk pappus bristles ca. 2 mm long, about half as long as disk corollas Leucosyris arida 8. Herbage homotrichous; involucres 6-8 > 10-15 mm; disk pappus bristles 3-3.5 mm long, more than half as long as disk corollas Leucosyris crispa 7. Herbage essentially glabrous to sparsely glandular. 9. Cauline leaves entire to shallow-toothed Leucosyris coulteri 9. Cauline leaves usually pinnatilobed to 2-pinnatifid Leucosyris parviflora (in part) LEUCOSYRIS ARIDA (B.L. Turner & D.B. Home) Pruski & R.L. Hartm., comb. nov. Machaeranthera arida B.L. Turner & D.B. Home, Brittonia 16: 324. 1964. Machaeranthera coulteri var. arida (B.L. Turner & D.B. Home) B.L. Turner, Phytologia 61: 144. 1986. TYPE: USA. California. San Bernardino Co.: Mesquite Valley, 15' May 1941, Wolf 10635 (holotype: DS; isotypes: CAS, NY, RSA, TEX-2, UC). Figure 1. Arida arizonica (R.C. Jacks. & R.R. Johnson) D.R. Morgan & R.L. Hartm.; Machaeranthera ammophila Reveal; Machaeranthera arizonica R.C. Jacks. & R.R. Johnson Annual low-rounded taprooted herbs 5-30(-40) cm tall; stems l(-6), moderately branched and leafy throughout, branches spreading-ascending; herbage densely short-stipitate-glandular, sometimes heterotrichous and also sparsely pilose-villous. Leaves: basal usually absent at anthesis; cauline 1-5 cm long, oblong in outline, margins entire to more commonly at least some pinnatilobed, apical mucro of lobes and teeth (usually 2-5 per side) about as iong as or slightly longer than the stipitate-giands. Capitula radiate; involucre 3.5-6 x 5-9 mm, hemispherical; phyllaries 2-4-seriate. Ray florets 20^10; corolla limb 5-8 mm long. Disk florets 28-60; corolla 4-6 mm long. Cypselae 1.4-2 mm long, rays epappose, disk pappus bristles ca. 2 mm long, about half as long as disk corollas. In = 10. Distribution. USA (Arizona, California, Nevada) and Mexico (Sonera); 0-1000 meters Turner and Home (1964) and Munz (1974) noted that the name Psilactis coulteri was often misapplied to Leucosyris arida (e.g., Hall 1907; Munz and Keck 1959; Ferris 1960). The mime Arida arizonica, based on the senior synonym, was used by Morgan and Hartman (2003) for this taxon. Line drawings of Leucosyris arida were provided by Ferris (I960, as Psilactis coulteri), Keil et al. (1993, as M. arida), Felger (2000, as M. coulteri var. arida), Hartman and Bogler (2006, as Arida arizonica), and Keil et al. (2012, as A arizonica). LEUCOSYRIS BLEPHAROPHYLLA (A. Gray) Pruski & RL. Hartm., comb. nov. Aster blepharophyllus A. Gray, Smithsonian Contr. Know!. [Plantae Wrightianae II] 5(6): 77. 1853. Machaeranthera gypsitherma Nesom, Vorobik & Hartman, Syst. Bot. 15: 638. 1990 (non M. blephariphylla (A Gray) Stunners, basionym in Haplopappus). Arida blepharophylla (A Gray) D.R.' Morgan & R.L. Hartm., Sida 20: 1413. 2003. TYPE: USA. New Mexico. Hidalgo Co.: Las Playas Springs. 7 Oct 1851, Wright 1164 (holotype: GH; isotypes, CGE, GH, MO, NY,P,PH,US). Figure 2. Pruski and Hartman: Synopsis of Leucosyris 5 Caespitose perennial rhizomatous herbs 4-35 cm tall; stems 4-12+ from woody crown, sparingly branched in distal half, branchlets somewhat fastigiate, erect-ascending; herbage glabrous or nearly so. Leaves dimorphic, basal and cauline; basal present at anthesis, in compact persistent rosette, sessile, 1-4 cm long, linear-spatulate, subsucculent, base clasping, margins entire, 8-20- spinulose-ciliate, spinules 0.4-1.5 mm long, subequal, sometimes as long as blade width; cauline abruptly reduced and scale-like. Capitula radiate; involucre 7-10 x 5-8 mm, turbinate; phyllaries 4- 6-seriate; receptacle often noticeable alveolate with lacerate borders to 0.5 mm tall. Ray florets 8- 14; corolla limb 8-10 mm long. Disk florets 12-20+; corolla 4.5-5.5 mm long. Cypselae 1.7-2.4 mm long, rays pappose. 2/7 = 10. i: Synopsis of Leucosyhs 6 J 48830 fe) .«,,. « r foUehzmfs Iwt A£o* tf,„„,-«^U+r./W #:*»* v c. 7;A^, f/uoaJL Pruski and Hartman: Synopsis of Leucosyris ~j Distribution. USA (New Mexico, Texas) and Mexico elevation. Leucosyris blepharophylla was described by Gray (1853) in Aster sect. Oxytripolium (DC.) Torr. & A Gray. The orthography of the epithet is retained as it may refer to the dense cloaking leaf rosettes or to leaves resembling sect. Blepharodon, although as likely it may refer to the leaves with marginal leaf spinules similar to those of African Blepharis Juss. (Acanthaceae). Nesom et al. (1990) provided a line drawing under the name of Machaeranthera gypsitherma. LEUCOSYRIS CARNOSA (A. Gray) Greene, Fl. Francisc. 384. (5 Aug) 1897. Linosyris carnosa A. Gray, Smithsonian Contr. Knowl. [Plantae Wrightianae II] 5(6): 80. 1853. Bigelowia carnosa (A Gray) Berth. & Hook, f, Gen. PI. 2: 255. 1873. Aster carnosus (A. Gray) A Gray ex Hemsl., Biol. Cent.-Amer., Bot. 2: 120. 1881 (non Gilib. 1781). Machaeranthera carnosa (A. Gray) G.L. Nesom, Phytologia 67: 439. 1989. Arida carnosa (A, Gray) D.R. Morgan & R.L. Hartm., Sida 20: 1413. 2003. TYPE: USA. Arizona. Cochise Co.: south of Willcox Playa [fide Sundberg 1986; protologue locality as "west of the Chiricahua Mts., Sonora" and collection number originally 489], 6 Sep 1851, Wright 1187 (holotype: GH; isotypes:GH, MO, PH, US-2). Figure 3. Aster intricatus (A Gray) S.F. Blake: Bigelowia intricata A Gray; Leucosyris carnosa var. intricata (A Gray) Cronquist; Machaeranthera carnosa var. intricata (A. Gray) Nesom Sparsely leafy to nearly leafless wiry-reedy or rounded and tumbleweed-iike perennial rhizomatous subshrubby herbs 0.3— 1(— 1.4) m tall; stems 1-several, moderately to intricately divaricate-branched throughout or only so somewhat above base, stiff, inconspicuously leafy distally, distal branches sometimes nearly fastigiate, ascending with branches and branchlets spreading, pale green; herbage glabrous and leaves glaucous. Leaves: basal absent at anthesis; cauline mostly distal, often quickly deciduous, spreading to nearly appressed, inconspicuous, well-spaced and scale-like, 0.3-2 cm long, narrowly lanceolate or narrowly oblanceolate, subsucculent, margins entire, apex apiculate. Capitula discoid; involucre 5-8 < 4-7 mm, turbinate to turbinate-campamilate; phyllaries strongly graduated, 4-6-seriate, dark mid-zone often narrow, some subcuspidate. Ray florets absent. Disk florets (5-)10-30(-40); corolla 5-7 mm long. Cypselae 2.5^1 mm long, pappose. 2n = 10. Distribution. USA (California, Aizona, Nevada) and Mexico (Sonora), often growing in otherwise basically barren ground; 100-1600 meters elevation. Gray (1852, 1853) treated eight species in Linosyris (20+ Anerican species have at onetime or another been placed in Linosyris), described ours as "L. ? carnosa," and mentioned that it looked like "a Tripolium without rays." Leucosyris carnosa (the generitype), especially the nearly leafless Bigelowia intricata phase, brings to mind leafless Chloracantha spinosa, also placed by Greene (1897b) into Leucosyris. However, the more widespread Chloracantha Nesom et al. ranges from Louisiana to California and south from Mexico and Guatemala to Costa Rica and western Panama, and differs from Leucosyris by a base chromosome number of x = 9, thorny stems, short-radiate capitula, and glabrous cypselae. Line drawings of Leucosyris carnosa w r ere provided by Ferris (1960, as Aster intricatus), Sundberg (1986, as L. carnosa), Cronquist (1994, as L. carnosa var. intricata). and Keil et al. (201 2, as Arida carnosa). i: Synopsis of Leucosyhs Figure 3. Isotype of Linosyris carnosa A. Gray (= Leucosyris carnosa (A. Gray) Greene). {Wright 1187, MO). Pruski and Hartman: Synopsis of Leucosyris 9 specimen of Leucosyris crispa (Brandegee) Pruski & R.L. Hartm. {Hartman et al Pruski and Hartman: Synopsis of Leucosyris 10 LEUCOSYRIS COULTERI (A Gray) Pruski & R.L. Hartm., comb. nov. Psilactis coulten A. Gray, Mem. Amer. Acad. Arts, n.s. [Plantae Fendlerianae] 4(1): 72. 1849. Machaeranthera coulteri (A Gray) B.L. Turner & D.B. Home, Brittonia 16: 322. 1964. Arida coulteri (A. Gray) D.R. Morgan & RL. Hartm., Sida 20: 1414. 2003. TYPE: MEXICO. Sonora. Probably near the coast by Guaymas, s.d., Coulter 295 (holotype: GH p.p., right-hand side; mounted on the same sheet towards the left is Gregg 409, which belongs to a different taxon). Wiry-reedy perennial taprooted herbs 15-45 cm tall; stems few-branched, weakly ascending to procumbent nearly leafy throughout or only distally so; herbage sparsely to moderately sessile- glandular (homotrichous) or stems nearly glabrous. Leaves: basal usually absent at anthesis; cauline 0.5-3 cm long, linear-lanceolate, margins entire to shallow-toothed. Capituia radiate; involucre 8- 10(-11) x 5-8 mm, hemispherical; phyllaries ca. 40, 3-5-seriate. Ray florets ca. 33; corolla limb 5- 8 mm long. Disk florets 40-60; corolla 3.5-4 mm long. Cypselae 1-1.5 mm long, rays (usually) epappose. 2n = 10. Distribution. Mexico (Sonora); 0-100 meters elevation. Leucosyris coulteri was one of the two original species, but not the type, of Psilactis A Gray (1849). LEUCOSYRIS CRISPA (Brandegee) Pruski & RL. Hartm., comb. nov. Psilactis crispa Brandegee, Proc. Calif. Acad. Sci., ser. 2, 2: 169. 1889. Machaeranthera crispa (Brandegee) B.L. Turner & D.B. Home, Brittonia 16: 321. 1964. Arida crispa (Brandegee) D.R. Morgan & R.L. Hartm., Sida 20: 1414. 2003. TYPE: MEXICO. Baja California Sur. San Ignacio, 1 Apr 1889, Brandegee s.n. (holotype: UC; isotypes: GH, PH, US). Fig. 4. Annual or short-lived perennial herbs 20-50 cm tall, from thick taproot; stems 1-few from base, ascending to erect, fairly leafy and moderately branched throughout, mid-stems homotrichous with stipitate-glandular trichomes, branches ascending; herbage densely stipitate-glandular, homotrichous. Leaves: basal absent at anthesis; cauline 0.5-4 cm long, linear-oblong, few- pinnatilobed about halfway to midrib, lobes (teeth) well-spaced. Capituia radiate; involucre 6-8 x 10-15 mm, hemispherical; phyllaries 3-5-seriate, apex sometimes spreading. Ray florets 30-40; corolla limb 6-8 mm long. Disk florets 40-60; corolla 3.8-6 mm long. Cypselae 2-2.4 mm long, rays usually epappose, disk pappus bristles 3-3.5 mm long, more than half as long as disk corollas. 2n = 10. Distribution. Mexico (Baja California Sur, Sonora; Leucosyris crispa was given as endemic to Baja California Sur by Slireve and Wiggins (1964) and Wiggins (1980), but Hartman (1976, 1990) and Felger (2000) gave it as also occurring in coastal Sonora; 50-170 meters elevation. LEUCOSYRIS MATTTURNERI (B.L. Turner & G.L. Nesom) Pruski & RL. Hartm., comb. nov. Arida mattturneri B.L. Turner & G.L. Nesom, Sida 20: 1418. 2003. TYPE: USA Texas. Presidio Co.: ca. 2.2 miles NNW of Ruidosa, 20 Jul 2003, Turner 100 (holotype: TEX; isotype: NY). Perennial subcaespitose taprooted herbs 50-80 cm tall, from persistent basal rosette; stems several, much-branched, erect or ascending, sparsely leafy, stiff; herbage sessile-glandular or short- stipitate-glandular, viscid. Leaves basal and cauline. surfaces densely glandular, basal rosette leaves persistent, 4-6 cm long, bipinnatifid, oblanceolate to broadly obovate in outline, basal ones abruptly grading into cauline, these linear-oblanceolate. 1-pinnatilobed to toothed or entire, ultimate ones scale-like. Capituia radiate; involucre 5-6 x 6-8 mm, hemispherical; phyllaries 5-6-seriate, oblong- Pruski and Hartman: Synopsis of Leucosyris \ \ lanceolate, at least the outer with apices spreading. Roy florets 9-13; corolla 10-12 mm long, limb 9-10 mm long. Disk florets 40-100; corolla 3.5-4.5 mm long. Cypselae 1-1.5 mm long, rays epappose. In = 10. adjacent Mexico (Chihuahua, Coahuila); 1400- Turner and Nesom (2003) provided both habit and floral photographs of Leucosyris LEUCOSYRIS PARVIFLORA (A. Gray) Pruski & R.L. Hartm., comb. nov. Machaer anther a parviflora A Gray, Smithsonian Contr. Knowl. [Plantae Wrightianae I] 3(5): 90, 1852. Aster parviflorus (A. Gray) A. Gray, Bot, California 1: 322. 1876 (nonA parviflorus Nees 1832). Aster parvulus S.F. Blake, Contr. U.S. Natl. Herb. 25: 563. 1925 (non A parviflorus Nees 1832). Arida parviflora (A Gray) D.R. Morgan & R.L. Hartm., Sida 20: 1414. 2003. TYPE: USA. New Mexico. Along the Rio Grande, Sep 1849, Wright 271 (holotype: GH; isotypes: BM,NY,P,US). Aster tanacetifoiius var. pygmaeus (A. Gray) A. Gray: Machaeranthera pygmaea (A Gray) Woot. & Standi. -.Machaer anther a tanacetifoiiavar. pygmaea A. Gray Annual, biennial, or short-lived perennial taprooted herbs 10-30(-40) cm tall; stems 1- several from sometimes woody taproot, moderate-branched and leafy throughout, erect or ascending; herbage glabrous to sparsely stipitate-glandular and then somewhat viscid. Leaves: basal absent at anthesis; cauiine 1-3 cm long, lanceolate to oblong, chartaceous, base often clasping, margins usually few-pinnatilobed to 2-pinnatifid (sometimes distal stem leaves nearly entire to shallowly pinnatilobed), the distal ones weakly spreading or more commonly ascending. Capitula radiate; involucre - *> 4-0 mm hum^phen^s] plrihues 3^1-ssriate, minutely glandular, apices mostly appressed; receptacle 2-7 mm diam. Ray florets 10-32; corolla limb 6-8 mm long. Disk florets 18- 40+; corolla 3.5-4.5(-5) mm long. Cypselae 1.5-2 mm long, rays pappose or epappose. In = 10. Distribution. USA (Arizona, Colorado, New Mexico, Texas, Utah) and Mexico (Chihuahua, Coahuila); 1100-1700 meters elevation. Leucosyris parviflora was illustrated by Martin and Hutchins (1988), Cronquist (1994), and Ivey (2003) as Machaeranthera parviflora. LEUCOSYRIS RIPARIA (Kunth) Pruski & R.L. Hartm., comb. nov. Aster riparius Kunth, Nov. Gen. Sp. (folio ed.) 4: 72. 1820[1818]. Machaeranthera riparia (Kunth) AG. Jones, Syst. Bot. 8: 85. 1983. Arida riparia (Kunth) D.R. Morgan & R.L. Hartm., Sida 20: 1414. 2003. TYPE: MEXICO. "Crescit in humidis juxta lacum Cuiseo" (given in Stearn 1968 as Cuitzeo and visited in Sep 1803, see below), Humboldt & Bonpland s.n. (4308) (holotype: P-HBK; isotypes: B-W 15821, P). Figure 5. Aster sonorae A Gray; Machaeranthera sonorae (A. Gray) Stucky Wiry-reedy annual taprooted herbs 25-60 cm tall; stems 1-several, moderately-branched distal in 2/3, erect to sometimes procumbent, leafy throughout, stiff, branches strongly ascending, sometimes striped (costae pale) longitudinally; herbage glabrous or nearly so. Leaves mostly cauiine, strongly ascending to distal ones nearly appressed, sessile, 0.5-3 cm long, oblanceolate, lanceolate to oblong, subsucculent, broad-based, margins entire, sometimes soft-ciliate, apex mucronate, Capitula i: Synopsis of Leucosyris \2 radiate; involucre 10-12 x 10-16 mm, hemispherical; phyllaries 5-8-seriate, some attenuate. Ray florets 30-50+; corolla limb 8-11 mm long, sometimes white. Disk florets (25-)40-80+; corolla 3.5-5 mm long, lobes sometimes long-triangular. Cypselae 2-3 mm long, rays pappose. In = 10. 3 A. Gray (= Leucosyris riparia (Kunth) Pruski & R.L. Hartm.). (Wri Pruski and Hartman: Synopsis of Leucosyris 13 Distribution. USA (Arizona arid New Mexico, where sometimes hybridizing, fide Stucky 1978 and Hartman 1990, with L. parviflora) and Mexico (Chihuahua, Coahuila, Durango, Zacatecas, ?Guanajuato); 900-2000 meters elevation. The protologue locality of Cuitzeo (as "Cuiseo") as given by Steam (1968) was visited by Humboldt and Bonpland in September 1803. Modern gazetteers list place names of Cuitzeo in Guanajuato, Jalisco, and Michoacan. The possible Humboldt and Bonpland type collection locality near Laguna de Cuitzeo seems to be between northern Mchoacan and Guanajuato, somewhat south of Durango and Zacatecas, the southern-most distribution of the species known to us. The northwestern-most Mexican localities visited by Humboldt and Bonpland are near Guanajuato (Stearn 1968), and McVaugh (1984) did not list this species for Novo-Galicia. We cannot place with any degree of certainty the type collection locality of Aster riparius. Stucky (1978) discussed seven hybrids in the Machaeranlhera group and noted that the highest pollen fertility observed was in hybrids between L. parviflora (as M. parviflora) and L. riparia (as Aster sonorae), prompting him to propose the combination M. sonorae. As noted by Morgan and Hartman (2003), the Stucky (1978) results strengthen the generic limits based on cpDNA evidence. Aster sonorae is usually treated in synonymy, but was resurrected by Turner et al. (1975), and reduced again by Jones (1983), LEUCOSYRIS TURNERI (ML. Arnold & R.C. Jacks.) Pruski & R.L. Hartm., comb. nov. Machaeranthera turner, ML. Arnold & R.C. Jacks., Syst. Bot. 3: 209. 1978[1979]. Arida turneri (M.L. Arnold & R.C. Jacks.) D.R, Morgan & R.L. Hartm., Sida 20: 1414. 2003. TYPE: MEXICO. Chihuahua. 3.3. miles N of Meoqui, 1 Aug 1964, Jackson 4005 (holotype: TTC). Annual taprooted herbs to 1.5 m tall; stems branched, proximal stems sometimes decumbent, leafy mostly in distal half; herbage stipitate-glandular. Leaves: basal usually absent at anthesis; caulrne usually deeply pinnatilobed and lanceolate in outline, chartaceous. Capitula radiate; involucre 7-10 x 10-17 mm, hemispherical; phyllaries 64-134, linear-lanceolate, apices spreading to reflexed; receptacle 8-11 mm diam. Ray florets 40-60; corolla 11-15 mm long. Disk florets 80- 150+; corolla 4.5-6 mm long. Cypselae ca. 2.5 mm long, rays pappose. In = 10. Distribution. Mexico (Chihuahua, Coahuila); 1100-1300 meters elevation. EXCLUDED SPECIES Leucosyris spinosa (Benth.) Greene, Pittonia 3: 244. (9 Dec) 1897. Basionym: Aster spinosus Benth. = Chloracantha spinosa (Benth.) G.L. Nesom, Phytologia 70: 378. 1991. ACKNOWLEDGEMENTS We would like to thank Guy Nesom, Rosa del Carmen Ortiz, George Yatskievych, and James Zarucchi for help and for reading and reviewing the manuscript. We are grateful to Stephanie Keil for talcing the specimen photographs. LITERATURE CITED Arnold, M.L. and R.C. Jackson. 1978[1979]. Biochemical, cytogenetic and morphological relationships of a new species of Machaeranthera sect. Arida (Compositae). Syst, Bot. 3: 208-217. 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