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ABSTRACfWoodson recognized two subgenera within Macrosiphonia (Apocynaceae: Apocynoideae), a South American subgenus Eumacrosiphonia, and a North American subgenus Telosiphonia each with five species. Both taxa are characterized by low subshrub-shrub, nonviny growth habits, white, long-tubed, vespertine corollas of a type associated with moth pollination. Their distinctive anther and style-tip characteristics show each is related to a group of genera around Mandevilla and Mesechites. The two subgenera, however, differ strongly from each other in inflorescence, style-head structure, and pollen size indicating that they are not sister taxa and that Macrosiphonia as currently recognized is polyphyletic. Thus the subgenus Telosiphonia is elevated to generic rank consisting of six species with one species and one variety described as new.

INTRODUCTIONThe Fouquieriaceae are small trees and shrubs native to arid portions of Mexico and southwestern United States . The family is treated as consisting of two genera: Fouquieria with 11 known species, and the monotypic Idria. For a brief description of the distribution, growth habits, and floral characteristics of the family, see Henrickson, 1969. Ever since the family has been known to science, only a small number of anatomical studies have been undertaken. Van Tieghem ( 1899), in reporting on material collected in Baja California by Diguet, made a general and relatively incomplete description of spine formation and stem and floral morphology. He claimed his findings provided evidence of an affinity of this family with the Ebenales. Solereder ( 1908) in his Systematic Anatomy of the Dicotyledons discussed the general anatomy of Fouquieria and included the genus in the Tamariscaceae, where it formed an aberrant element. He included a discussion of leaf, spine, and wood anatomy. In 1922 Reiche published an account of the vegetative and floral anatomy and morphology of Fouquieria formosa. His work was based on study of preserved materials, and was the first to describe accurately the stem cortex, spines, etc. Scott ( 1932) discussed various features of the anatomy of F ouquieria splendens and carefully described the stem cortex and periderm. In 1935 Humphrey made a detailed study of the morphology of Idria columnaris and described the structure of the main trunk and secondary branches. More recently, Metcalf and Chalk ( 1950) presented a general review of the peculiar morphology of the family, including a brief description of the xylem.The spines of the Fouquieriaceae are formed in association with the longshoot leaves. Several authors have reported on this peculiar method of spine formation (

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