Galinsoga subdiscoidea Cronquist

Authority

Cronquist, Arthur J. 1965. Studies in Mexican Compositae. I. Miscellaneous new species. Mem. New York Bot. Gard. 12: 286-292.

Family

Asteraceae

Scientific Name

Galinsoga subdiscoidea Cronquist

Type

Type. Cronquist 9583, in thin soil on rhyolite rock in open pine woods; Sierra Madre Occidental, about 10 miles west of El Salto, state of Durango, Mexico. Elevation about 8800 feet. October 2, 1962. Holotype at NY; isotypes at F, GH, MEXU, MICH, TEX, US, others.

Description

Latin Diagnosis - Planta annua depressa 2-5 cm alta caulibus obscure strigosis puberulisve, foliis glabris integris subintegrisve oblanceolatis spathulatisve vel ellipticis usque ad 22 mm longis 8 mm latis vix petiolatis; capitula virido-lutea discoidea vel floseulum unicum femineum vix ligulatum habentia, involucro 3 mm alta achaeniis nigris pappo ex squamellis 10 bene evolutis ca. 1 mm longis ad apicem obtusis truncatisve et ciliolatis composite.

Species Description - Depressed annual only 2-5 cm tall, simple or branched; stem and peduncles thinly and inconspicuously strigose or puberulent, the plants otherwise glabrous; leaves all opposite, entire or nearly so, oblanceolate or spatulate to elliptic or narrowly rhombic, tapering to a narrow and sometimes more or less petiolar base, but not with a definite petiole, up to about 22 mm long and 8 mm wide, tending to be 3-nerved, the uppermost ones smaller and relatively narrower than the others; heads axillary and terminal, on short peduncles up to about 8 mm long, or some of them subsessile, greenish-yellow, discoid or with a single small, inconspicuous, scarcely ligulate pistillate flower, campanulate to hemispheric, the disk mostly 3-5 mm wide, involucre ca. 3 mm high; achenes obconic, black; pappus of about 10 well developed blunt scales a little shorter than the disk corollas, minutely fringed-ciliate distally, that of the pistillate flower similar to that of the disk flowers.

Discussion

This species is perhaps most closely related to G. semicalva (Gray) St. John & White, which was collected at the same time at the same station but is amply distinct. G. subeliscoidea differs from all other species of Galinsoga in its diminutive habit, in its scarcely petiolate leaves, and in its mostly discoid heads, which are scarcely radiate even when a solitary pistillate flower is present. It is also unusual in being nearly glabrous, although G. semicalva approaches it in this respect. It further differs from G. semicalva in that the pistillate flower, when present, has a pappus like that of the disk flowers, whereas in G. semicalva the ray pappus is much reduced. The peculiar greenish-yellow color of the disk flowers is also different from the more definite yellow of those species of Galinsoga which I have observed in the field. The plant is nonetheless a true Galinsoga, and no other genus could be stretched to accommodate it.