230 ASCLEPIADACEiE. 



ASCLEPI AS. —Milkweed. 



Character of the Genus. — Calyx 5-parted, j^ersistent, the lobes smaU, 

 spreading. Corolla deeply 5-parted, the lobes bent downward toward the 

 stalk ; within the petals are 5 hooded processes, each with an incurved 

 horn, forming what is called the crown, and enclosing the stamen-tube. 

 Stamens 5, inserted in the base of the corolla ; filaments united into a tube 

 which encloses the pistil ; anthers adherent to the stigma, each with 2 

 vertical cells, each cell containing a flattened pear-shaped mass of pollen. 

 Ovaries 2 ; styles united ; stigma 1, fleshy, 5-angled. Follicles 2, one of 

 them often abortive, ovate or somewhat curved, spindle-shaped ; seeds nu- 

 merous, tufted with soft silky hairs. 



Perennial herbs with thick, deep-growing roots. Flowers terminal or 

 lateral in simple, many-flowered umbels. 



Asclepias cornuti Decaisne {A. Syriaca Linne). — Milkweed, Silkweed. 



Description. — Hoods of the crown ovate, obtuse, with a lobe or tooth 

 on each side of the short and stout horn. Pods ovate, woolly, and rough, 

 with soft spines. Stem simple, erect, stout, 3 to 4 feet high. Leaves oj)- 

 posite, oblong-ovate, with short petioles, smooth above, minutely downy 

 beneath, pale green. Umbels manj'-flowered, terminal and lateral in 

 pedicels shorter than the leaves ; flowers greenish-purple, appearing in 

 midsummer. 



Habitat. — Common everywhere. 



Asclepias incarnata Linne. — Swamp Milkweed. 



Description. — Hoods of the crown scarcely as long as the slender, 

 pointed horn. Pods commonly smooth and glabrous. Stem erect, branch- 

 ing, 2 to 3 feet high, leafy to the tojD. Leaves opposite, oblong-lanceolate, 

 acute or pointed, obtuse or obscurely cordate at the base, with short peti- 

 oles. Umbels numerous, erect, mostly terminal, often in opposite pairs ; 

 flowers rose-purple, appearing in midsummer. 



A somewhat variable species, sometimes more or less hairy-pubescent, 

 again nearly smooth. 



Habitat. — Li wet, swampy places ; common. 



Asclepias tuberosa Linne, — Butterjiyweed — Pleurisy-Root. 



Description. — Hoods of the crown narrowly oblong, scarcely longer than 

 the nearly erect, slender, i^ointed horns, bright orange ; corolla lobes 

 greenish-orange. Pods lanceolate, hoary. Stems numerous from a large 

 fleshy rhizome, 1 to 2 feet high, very leafy. Leaves numerous, scattered, 

 some of them opposite, oblong-lanceolate or linear, sessile or short-petioled. 

 Umbels corymbose at the summit of the stem and branches ; flowers very 

 showy, ajDpearing late in summer. 



Habitat. — In dry fields, and along roadsides ; common southward. 



Part Used. — The root of A. tuberosa — United States Pharmacopoeia. 

 The roots of A, incarnata and A. cornuti were formerly official, but were 



