196 Swallow-wort, or SilJcweed. 



ASCLEPIAS— SWALLOW-WORT, OR SILKWEED. 



Natural Order, Asclepiadacese ; Liutuean System, Pentandria, Digy n u 

 Generic Distinctions: — Calyx, small; petals, united at base, reflexed- co. 

 rona, (nectary,) five-lobed, with five averted horns at the base of th 

 lobes ; antheridinm, (connate mass of anthers,) five-angled, truncate 

 opening by five longitudinal fissures ; pollinia, (masses of pollen,) in f lv » 

 distinct pairs ; follicles, two, ventricose ; seeds, comose. 



A. tuberosa. — Hairy ; branches, spreading at the summit ; leaves, distant 

 alternate, oblong-lanceolate; umbels, numerous, sub-corymbose, termi 

 nal.— P/.29. Fig. 1. 



Asclepias is the Greek name of Esculapius, the god of 

 medicine and physicians, and was applied to the plants of 

 this' genus, in reference to their supposed sanitary virtues. In 

 some respects, these plants are very curious. All of them are 

 filled with a milky juice, which, when the stem is broken 

 flows most copiously, and abounds in the substance called 

 caoutchouc, or Indian Rubber. The most common American 

 species, A. syriaca, is well known from its juice, which is re- 

 puted to cure warts, and is usually called Milkweed. There 

 are about ten or twelve native northern species, several of 

 which are very ornamental. Of these, the one which forms 

 the subject of our plate is the most showy, neat, and beautiful. 

 It is commonly called Butterfly-weed, from the circumstance 

 of its flowers being great favorites with the Butterflies, and 

 often covered with those elegant insects. The construction of 

 its flowers is very singular, and the description of them in the 

 following notice of the plant, by Dr. Bigelow, will guide the 

 student in his examination of other species, the flowers of all 

 having the same peculiarities. 



The root of this plant is large, fleshy, branching, and often 

 fusiform. It is only in comparison with the other species, that 

 it can be called tuberous. The stems are numerous, growing 

 in bunches from the root. They are erect, ascending, or pro- 

 cumbent, round, hairy, green or red. Leaves scattered, the 

 lower ones pedunculated, the upper ones sessile. They are 

 narrow, oblong, hairy, obtuse at base, waved on the edge, and 

 in the old plants sometimes revolute. The stem usually divides 

 at the top into from two to four branches, which give off 



