Psorothamnus emoryi

Title

Psorothamnus emoryi

Authors

Rupert C. Barneby

Scientific Name

Psorothamnus emoryi (A.Gray) Rydb.

Description

6.  Psorothamnus emoryi (Gray) Rydberg

(Plates V, VI)

Early suffrutescent herbs, rarely flowering prematurely as herbaceous annuals, commonly becoming rounded shrubs or subshrubs 3-10 dm tall and up to twice as wide, most often densely and softly tomentulose throughout with fine, spreading or sub- retrorse, ± entangled hairs up to ± 0.2-0.4 mm long, rarely the stems alone or both stems and foliage together glabrescent to fully glabrous, these then deep green and dotted all over with reddish-orange glands (always present, but here revealed), the foliage drought-deciduous, the plant becoming in dry seasons ± junceous and cancel- late; leaf-spurs almost 0; stipules subulate, 0.6-1.1 mm long, commonly tomentulose, charged on margins with a pair of orange glands, caducous; intra-petiolular glands 0; post-petiolular glands small but prominent, sometimes concealed by woolly vesture; leaves polymorphic and variable both from one plant to another and according to position on the stem, the main cauline ones usually with 2-4 (6) pairs of lateral leaflets varying from suborbicular-emarginate to oblong-oblanceolate or elliptic and from 2 to 10 mm long, the terminal leaflet always longer, usually narrower, obovate to oblanceolate or sublinear, mostly 4-16 (20) mm long, all flat or nearly so, the margins either entire or crenulate-dentate, gland-charged on both faces but the glands often concealed by vesture, the upper (sometimes all) leaves shorter and simpler, 3-folio- late or reduced to a subsessile blade, the uppermost often minute and bracteiform; peduncles leaf-opposed and terminal to all ultimate branchlets, 0.5-12 cm long; spikes dense, mostly capitate and subglobose, rarely oblong, without petals 7.5-13 (15) mm diam, the pilosulous axis becoming (1) 3-20 mm long; bracts early deciduous, narrowly lance-elliptic or subulate to sublinear, 1.5-3 mm long, pilosulous dorsally, the margins usually charged with 1-3 pairs of subulate orange glands; pedicels 0 (rarely to 0.2 mm long); bracteoles represented by 2 minute orange spicules; calyx (2.7) 3-6.6 (7.2) mm long, pilosulous with fine weak ascending hairs up to 0.4-0.8 mm long, the golden-yellow tube 1.7-3.4 mm long, its ribs slender becoming prominent, the intervals charged with 1-2 rows of small orange glands, the 1-nerved teeth varying from lance-acuminate to ovate-triangular and from ± 1 mm shorter up to 1 mm longer than tube, all gland-tipped and -spurred, the sinus behind the banner sometimes shallower than the rest; petals (deciduous) usually bicolored, the banner-blade margined and the inner petals banded along inner half with vivid purple or violet, otherwise paler or whitish, the blades of banner, keel, and often of wings also, pilosulous externally in distal 1/2-1/3; banner 4.2-6.3 mm long, the claw 1.6-2.3 mm, the ovate-cordate, apically emarginate blade 2.8-4.8 mm long, 2.4-4.1 mm wide, charged near apex dorsally with a prominent blister-gland; wings 5.2-7.8 mm long, the claw 1.6-2.6 mm, the narrowly oblong or oblong-oblanceolate, gland-tipped blade (3.5) 3.8-5.2 mm long, 1.3-1.8 mm wide; keel 5.7-8.5 mm long, the claws 1.7-3.3 mm, the obliquely oblong- obovate or broadly obovate blades 3.7-6.2 mm long, (2) 2.2-2.9 mm wide, usually glandless; androecium 5.7-7.8 mm long, the connective gland-tipped, the anthers 0.5-0.9 mm long; stigma slightly enlarged, subcapitate; pod subsymmetrically obovoid- ellipsoid, 2.3-2.8 mm long, cuneately narrowed and glabrous at base, pilosulous and gland-sprinkled distally, the style-base terminal; seed (little known) ± 1.5 mm long, the testa smooth, brown, dull, paler at the hilum and sometimes with a fuscous line above it.

I adopt here the comprehensive definition of Ps. emoryi proposed (under Dalea) by I. Johnston (1924, pp. 1046-7). While in full agreement with Johnston that five species of Psorothamnus from the Sonoran Desert maintained by Rydberg (Ps. emoryi, tinctorius, dentatus, arenarius, and junceus) can readily be accommodated in one, I differ in my view of the internal racial situation. Johnston referred all tomentose plants of this type to a typical variety of wide dispersal, but recognized two glabrescent or glabrate varieties, a northern var. junceus and a southern var. arenarius. With more extensive material now available, it appears that these pubescence-variants are unstable and reasonably treated as taxonomically unimportant formae, although it cannot be denied that they are visually striking. In this connection Dr. A. Carter’s observations of the southern glabrate form known as var. arenaria, as this grows on El Mogote peninsula in La Paz bay, are especially significant. Here a canescently woolly form was found at both ends of the peninsula and a glabrous one in the middle, the plants (Carter 2716, 2730, 2744, all UC) being otherwise essentially similar. Forms of Ps. emoryi with glabrate stems but foliage still tomentulose have been found growing close to fully glabrate individuals in the neighborhood of Bahia de los Angeles. The division of Ps. emoryi into a northern and southern variety, each of which presents a glabrescent phase, follows lines already drawn by Wiggins (1940, pp. 48, 49, pp. VIII); Wiggins treated these geographic entities as species, but I have found no reliable single differential character by which to distinguish them. As a rule the northern var. emoryi has a longer calyx, with absolutely and proportionately longer teeth of narrower outline; and the sinus between the pair of dorsal calyx-teeth is characteristically shallower than in its southern counterpart, var. arenarius. The petals of var. emoryi are vivid pink-purple, those of var. arenarius violet or bluish-purple. The adult plant of var. emoryi is genuinely shrubby, although the young growth may be soft and pliant, whereas the common forms of var. arenarius in the Cape region are herbaceous, flowering precociously and perhaps less enduring. There are exceptions, however, and intermediate forms. In Baja California Sur northward from La Paz the calyx and petal-color of var. arenarius is often combined with a shrubby habit, while in one Sonoran station at Kino Point (Johnston 4286; Wiggins & Rollins 169, both NY) the small calyx of var. arenarius is combined with the rose-purple coloring as well as the fruticose habit of var. emoryi. The collective range of all forms of Ps. emoryi extends without interruption from Coachella Valley in the north to Bahia La Paz in the south, a zone of transition between var. emoryi and var. arenarius occurring about midway down the Peninsula in latitudes 26° 30'-28° 30'.