Vol. ill.] 



MILKWEED FAMILY. 



I. ASCLEPIAS L, Sp. PI. 214. 1753. 

 Perennial erect or decumbent herbs, with opposite verticillate or rarely alternate entire 

 leaves, and middle-sized or small flowers in terminal or axillary umbels. Calyx 5-parted or 

 5-divided, usually small, the segments or sepals acute, often glandular within. Corolla 

 deeply 5-parted, the segments mostly valvate, reflexed in anthesis. Corona-column gener- 

 ally present. Corona of 5 concave erect or spreading hoods, each bearing within a slender 

 or subulate incurved horn, either included or exserted. Filaments connate into a tube; anthers 

 tipped with an inflexed membrane, winged, the wings broadened below the middle; pollen- 

 masses solitary in each sac, pendulous on their caudicles. Stigma nearly flat, 5-angled or 

 5-lobed. Follicles usually thick, acuminate. Seeds comose in all but one species. [Dedi- 

 cated to AEsculapius.] 



About 85 species, mostly natives of the New World: besides the following some 25 others occur 

 nnttiprn utiH mpttpm Mnrtli A.ipnVa Known as Milkweed, Silkweed, or Swallow-wort. 



in southern and western North America. 



-X- Corolla and corona orange ; leaves alternate or opposite 



i. A. tuberosa. 

 2. A. decumbens. 



A. 

 A. 

 A. 



A. 

 A. 



lanceolata. 



rubra. 



purpurascens. 



incarnata. 

 pulchra. 



Stem erect or ascending; leaves nearly all alternate. 



Stems reclining; leaves, at least the upper, opposite, oblong or oval. 



K- -X- Corolla bright red or purple ; leaves opposite. 

 Flowers 4"-6" broad; corona-hoods 2"-t," high. 



Leaves lanceolate or linear; hoods oblong, obtuse. 3. 



Leaves ovate or ovate-lanceolate; hoods lanceolate. 4. 



Leaves oblong, ovate or ovate-oblong; hoods oblong, acutish. 5. 



Flowers 2"-$" broad; corona-hoods i"-i%" high. 



Plant nearly or quite glabrous; leaves lanceolate or oblong-lanceolate. 6. 

 Plant pubescent; leaves oblong. 7. 



X- -X- vr Corolla greenish, purplish, yellowish or white ; leaves opposite or verticillate. 

 Leaves ovate, oblong, ovate-lanceolate, obovate or orbicular. 

 Plants glabrous throughout, or minutely pubescent above. 

 Leaves sessile, clasping or very short-petioled. 



Peduncles of the solitary or several umbels short. 



Leaves ovate-oblong; hoods 2-auriculate at the base 

 Leaves nearly orbicular; hoods truncate. 

 Peduncle of the usually solitary umbel elongated. 

 Leaves cordate-clasping, wavy-margined. 

 Leaves sessile, flat; horn not exceeding the hood. 

 Leaves manifestly petioled. 



Corolla greenish; umbels loose, the pedicels drooping. 

 Corolla white; umbels dense. 



Corolla pink; some of the leaves verticillate in 4's. 

 Plants, at least the lower surfaces of the leaves, canescent or tomentose. 

 Follicles tomentose, covered with soft spinose processes. 

 Corona-hoods obtuse, short. 

 Corona-hoods elongated, lanceolate. 

 Follicles with no spinose processes, glabrous or pubescent. 



Leaves wavy-margined; corolla-segments 4"~5" long. 17. A. arenaria. 



Leaves flat; corolla-segments 2" -3" long. 18. A. ovalifolia. 



Leaves lanceolate, oblong-lanceolate or linear. 



Leaves opposite, lanceolate or oblong-lanceolate. 



Leaves thick, short-petioled; inflorescence woolly. 19. 



Leaves thin, slender-petioled; inflorescence downy. 20. 



Leaves mostly verticillate in 3's-6's, narrowly linear. 21. 



Leaves scattered, densely crowded, filiform-linear. 22. 



10. 

 n. 



12. 



13- 



14. 



15- 

 16. 



17. 



18. 



A. Sullivantii. 

 A. latifolia. 



A. obtusifolia. 

 A. Meadii. 



A. exaltata. 

 A. variegala. 

 A. quadrifolia. 



A. 

 A. 



Syriaca. 

 speciosa. 



A. brachy Stephana. 

 A. perennis. 

 A. verticillata. 

 A. pumila. 



i. Asclepias tuberosa L. Butterfly- 

 weed. Pleurisy-root. (Fig. 2900.) 



Asclepias tuberosa L. Sp. PI. 217. 1753. 



Hirsute-pubescent; stems rather stout, simple, 

 or branched near the summit, ascending or 

 erect, very leafy, i-2 high, the milky sap 

 scanty. Leaves usually all alternate, lanceo- 

 late or oblong, acute or sometimes obtuse at the 

 apex, narrowed, rounded or cordate at the base, 

 sessile or short-petioled, 2 / -6 / long, 2"- 

 I2 r/ wide; umbels cymose at the ends of the 

 stem or branches, many-flowered; peduncles 

 shorter than the leaves; pedicels pubescent, 

 Yz'-\' long; corolla-segments oblong, obtuse, 

 about 3 // long, greenish orange; corona-column 

 about y 2 " long; hoods erect, oblong, bright 

 orange, or rarely yellow, 2-3 times as long as the 

 stamens, slightly longer than the filiform horns; 

 fruiting pedicels decurved; follicles nearly erect, 

 finely pubescent, 4 / -5 / long. 



In dry fields, Maine and Ontario to Minnesota, 

 Florida, Texas and Arizona. June-Sept. Called 

 also Wind-root, Orange-root. 



