Trixis

• Authority

  Anderson, Christiane. 1972. A monograph of the Mexican and Central American species of Trixis (Compositae). Mem. New York Bot. Gard. 22: 1-68.

• Family

  Asteraceae

• Scientific Name

  Trixis

• Description

  Species Description - Perennial, erect or traihng shrubs. Pubescence composed of uniseriate glandular and nonglandular hairs; glandular trichomes either 30-100(-150) µ, long, ascending and not tapered, or (120-) 150-300(-400) jx long, erect and tapered; nonglandular hairs with 1-8 roughly cubic basal cells and an elongate tapered apical cell. Rhizomes horizontal, woody, covered with fissured bark, sometimes with villous buds. Aerial stems 0.5-2.5(-4) m tall, terete, slightly ribbed, commonly much branched, sometimes vdnged, bearing prominent persistent leaf bases, glabrous or nearly so but young branches and inflorescence pubescent. Leaves alternate, petiolate, subsessile, or sessile; blades simple, usually flat except at the margins (the whole blade commonly inrolled in T. angustifolia), several times as long as wide, linear to linear-lanceolate to lanceolate to elhptical to ovate to oblanceolate to oblong to obovate, acute or acuminate at the apex, attenuate or subtruncate at the base, sometimes decurrent and continuous with the stem wings, strigose to sericeous to wooly and usually glandular, rarely glabrous or with only a few hairs, margins irregularly denticulate, especially in the larger leaves, or entire, rarely serrate, usually shghtly recurved or revolute, rarely flat; venation reticulate, the midrib and nerves usually prominent beneath; cells of the epidermis with wavy or straight cell walls, commonly containing needle-shaped crystals and crystal sand; stomates ranunculaceous, restricted to the lower surface except in T. californica var. californica which is amphistomatic. Inflorescence terminal, usually compound (corymbose or paniculate), the heads rarely solitary at the tips of branches in T. californica and T. angustifolia; heads cylindrical, pedunculate or subsessile. Involucre subtended by 1-12 (commonly 3-5) accessory bracts, these ascending and then often enveloping the head, or spreading or reflexed, usually linear, linear-lanceolate, lanceolate or ovate (but sometimes elliptical, oblanceolate, oblong or obovate), acute, acuminate or aristate at the apex, short-petiolate or sessile, strigose or pilose, rarely sparsely sericeous or glabrous, often glandular, margins entire, flat, shghtly recurved or revolute; venation reticulate, midrib often prominent beneath. Phyllaries 8 or rarely 5 and uniseriate, or 13 or rarely 16 and biseriate, usually equal in length, linear, oblong, or subulate, convex or keeled, erect in flowering heads but spreading or reflexed in old fruiting heads, with a prominent basal callus, the distal one-third or half herbaceous, adaxially strigose, rarely glandular, the proximal portion cartilaginous, glabrous on the adaxial surface, the abaxial surface strigose, sericeous or wooly, usually glandular, rarely glabrate or glabrous; margins pubescent and tightly appressed to one another; midrib and nerves often prominent abaxially. Receptacle flat, alveolate, the shallow depressions separated by ridges bearing short stiff persistent hairs. Flowers hermaphroditic, all fertile, usually 11-14 or 18-22(-29) ca. 60 in T. alata, 4-6 in T. pringlei var. oligantha; the inner flowers similar to the outer ones but usually smaller. Corolla yellow but white in age, including numerous druse crystals especially in the tube, bilabiate, with five fused lateral veins, the venation often reduced in the distal portion of the lips; tube slender, the inner surface with short hairs in the distal one-third or half, the outer surface glabrous or glandular or rarely also with a few nonglandular hairs on the distal half or quarter; outer hp elliptical or oblong, usually spreading but sometimes revolute in the outer flowers, always revolute in the inner flowers, the inner surface glabrous, the outer surface glabrous or glandular and often with a few nonglandular hairs, the apex three-toothed, papillose on the inner surface and the margins, hispidulous on the outer surface; inner lip bifid, each lobe revolute at maturity, glabrous on the inner surface, glabrous or glandular and often with a few nonglandular hairs on the outer surface, the apex acute, papillose on the inner surface and on the margins, hispidulous on the outer surface. Stamens five, the filaments inserted at a point onehalf or two-thirds from the base of the tube; anthers connate, with oblong apical appendages, tailed at base, partially exserted in the mature flower; pollen grains prolate, tricolporate, ca. 30-40 µ, long. Style with a knobby basal thickening, including numerous druse crystals, unbranched for four-fifths of its length; style branches flattened, truncate and with a crown of sweeping hairs at the apex, papillose on the adaxial surface, glabrous on the abaxial surface, slightly recurved to almost revolute at maturity. Achenes fusiform with a short beak or an apical constriction, five-ribbed, black at maturity, covered with colorless double hairs (ca. 150-200 µ, long) that release mucilage when wetted (except in T. inula) and with small glands (30-80 µ long), these especially dense on the beak; embryo straight, 50-60(-90)% of it composed of the cotyledons. Pappus of numerous (over 150) hispidulous, tawny or white bristles in three or four series.

• Discussion

  Type: T. inula Crantz.