Asclepias N. F. IV. Butterfly weed. Pleurisy root.—This is described in the N. F. as "the dried roots of Asclepias tuberosa Linne (Fam. Asclepiadaceae), without the presence of more than 6 per cent. of foreign matter. Usually cut or broken pieces, of variable size, of an irregularly fusiform root, which, when entire is from 10 to 20 cm. in length and from 0.5. to 5 cm. in thickness; occasionally branched; externally pale orange-brown, becoming grayish-brown, annulate above, the surface roughened by numerous fine intersecting grooves; bark thin; fracture tough, the broken surface granular and white, with inconspicuous pale yellow wood bundles and large white medullary rays. Odor slight; taste bitterish and disagreeable, somewhat acrid. The powdered drug is yellowish-brown and, when examined with the microscope, shows numerous simple or two- to four-compound starch grains, the individual grains up to 0.015 mm. in diameter, somewhat spherical in shape, or truncate and often with a cleft at center; calcium oxalate crystals in rosette aggregates up to 0.04 mm. in diameter; strongly lignified thick-walled stone cells up to 0.075 mm, in diameter and with simple or branching pores; tracheae with reticulate markings, occasionally bordered porea; spindle-shaped sclerenchyma fibers few, lignified and mostly with simple pores. Asclepias yields not more than 9 per cent. of ash." N. F. It grows from Ontario to Minnesota, most abundantly southward and southwestward. It contains a glucosidal principle, Asclepiadin, which occurs as an amorphous body, is soluble in ether, alcohol and hot water. It also contains several resins and a trace of volatile oil. Besides the American species Asclepias tuberosa, A. syriaca, and A. incarnata, which were formerly recognized by the U. S. Pharmacopoeia, various other species of the genus have been used medicinally.
To the root of the A. tuberosa, have been ascribed diaphoretic, expectorant, and cathartic properties. In the Southern United States the drug has been given in pulmonic catarrhs in doses of from twenty grains to a drachm (1.3-3.9 Gm.) in a powder or in the form of a decoction; as a diaphoretic, a teacupful of the decoction (1 in 30) every hour until some effect is produced. For additional information concerning Asclepias species, see U. S. D., 19th ed., p. 1400.