A Revision of Samolus ebracteatus (sensu lato) (Primulaceae)

Abstract

A revision of the Samolus ebracteatus-cuneatus complex is presented recognizing five varieties of S. ebracteatus: S.e. var. ebracteatus from the Caribbean and Florida; var. alyssoides from coastal Texas to Mexico; var. cuneatus from inland Texas to Nevada and central Mexico; var. coahui- lensis (var. nov.) from central Coahuila; and var. breviflorus (var. nov.) from southern Mexico. Preparation of a treatment of Samolus L. for M. C. Johnston's Chihuahuan Desert Flora has lead to this revision of the entire Samolus ebracteatus-cuneatus complex. This was necessary to properly accommodate a new taxon from central Coahuila. Three taxa have been described within this complex. All are relatively similar in vegetative and floral characteristics (Fig. 1) and distinguished from other species in the genus by the absence of bracts on pedicels and absence of distinct epipetalous staminodia attached to the corolla tube and alternate to its lobes (Pax and Knuth, 1905). Samolus ebracteatus was described by Kunth (1815) from a collection by Humboldt and Bonpland from southern Cuba near Batabano, south of Havana. While the original description and illustration make no note of stipitate glands, study of other specimens from the type locality indicate that material from Cuba, Florida, and the West Indies are all similar and characterized by stipitate glands on pedicels, inflorescence axes, and moderately large, mostly pinkish-white corollas. A second taxon, S. alyssoides was described by Heller (1895) from a sandy habitat along the east coast of Texas. He distinguished the new species from S. ebracteatus on the basis of growth habit, emphasing its erect, more compact nature in contrast to a more leafy, spreading habit of S. ebracteatus. He also noted the new taxon had glaucous leaves and larger flowers than S. ebracteatus. Though not noted by Heller, S. alyssoides differs from Floridian-West Indian populations of S. ebracteatus by the lack of stipitate glands on pedicels and inflorescence axes. In that paper, Heller (1895) also cites a collection of S. ebracteatus from near Kerrville, Texas which he apparently had used to contrast his S. alyssoides. He distributed the specimens of that collection identified as a new species, but never published the new name. In 1897 Small cited Heller's Kerrville specimen as the type of a new species S. cuneatus noting it could be distinguished from S. ebracteatus and S. alyssoides by its smaller flowers measuring only 4-5 mm (not 6-9 mm) in breadth and by its more cuneate (not suborbicular) petal lobes. Like the Floridian-West Indian specimens of S. ebracteatus it also has stipitate glands on the pedicels and inflorescence axes.