24 ASCLEPIADACEAE. Vor. LIL. | 
bases to the filaments, introrsely 2-celled, connivent around the stigma, or more 
or less united with each other ; anther-sacs tipped with an inflexed or erect scarious 
membrane, or unappendaged at the top, sometimes appendaged at the base; pollen 
coherent into waxy or granular masses, one or rarely two such masses in each sac, 
connected with the stigma in pairs or fours, by 5 glandular corpuscles alternate with 
the anthers. Disk none. Ovary of 2 carpels; styles 2, short, connected at the 
summit by the peltate discoid stigma; ovules numerous in each carpel, mostly 
anatropous, pendulous. Fruit of 2 several-many-seeded follicles. Seeds com- 
pressed, usually appendaged by a long coma; endosperm cartilaginous, mostly 
thin ; embryo nearly as long as the seed ; cotyledons flat. 
About 220 genera and 2000 species, of very wide geographic distribution, most abundant in 
tropical or warm-temperate regions. 
Erect or decumbent herbs. 
Corona-hoods each with an incurved horn within; eaves mostly opposite. 1. Asclepias. 
Corona-hoods prominently crested within; leaves alternate. 2. Asclepiodora. 
Corona-hoods unappendaged or with a thickened crest-like keel. 3. Acerates. 
Twining vines. 
Corolla-lobes erect ; corona-lobes 1-2-awned. 4. Gonolobus, 
Corolla rotate. 
Anthers tipped with a scarious membrane; pollen-masses pendulous, 5. Cynanchum. 
Anthers merely tipped ; pollen-masses horizontal. 7 6. Vincetoxicum. 
1. ASCLEPIAS L. Sp. Pl. 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 generally 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 acuminate. Seeeds comose in all but one species. [Dedicated to Aesculapius.] 
About 95 species, mostly natives of the New World:; besides the following, some 25 others occur 
in southern and western North America. Known as Milkweed, Silkweed, or Swallow-wort. Type 
species: Asclepias syriaca L. 
* Corolla and corona orange; leaves alternate or opposite. 
Stem erect or ascending ; leaves nearly all alternate. 1. A, tuberosa. 
Stems reclining ; leaves, at least the upper, opposite, oblong or oval. 2. A. decumbens. 
** Corolla bright red or purple (sometimes greenish in A. rubra) leaves opposite. 
Flowers 4”—-6” broad; corona-hoods 2”-3” high. 
Leaves lanceolate or linear; hoods oblong, obtuse. 
Leaves ovate or ovate-lanceolate ; hoods lanceolate. 
Leaves oblong, ovate or ovate-oblong; hoods oblong, acutish. 
Flowers 2”-3” broad ; corona-hoods 1”-114” high. 
Plant nearly or quite glabrous ; leaves lanceolate or oblong-lanceolate. .» A. incarnata, 
Plant pubescent ; leaves oblong. . A. pulchra. 
*** 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. 8. A. Sullivantii. 
Leaves nearly orbicular ; hoods truncate. 9. A, latifolia, 
Peduncle of the usually solitary umbel elongated, 
Leaves wavy-margined. 
. A. lanceolata, 
. A.rubra. 
. A, purpurascens, 
NN Mhw 
Leaves cordate-clasping. 10. A. amplexicaulis, 
Leaves rounded at the base, short-petioled. 11. A, intermedia, 
Leaves sessile, flat; horn not exceeding the hood. 12, A. Meadii, 
Leaves manifestly petioled. 
Corolla greenish; umbels loose, the pedicels drooping. 13. A. exaltata. 
Corolla white ; umbels dense. 14. A. variegata, 
Corolla pink; some of the leaves verticillate in 4’s. 15. A. quadrifolia, 
Plants, at least the lower surfaces of the leaves, canescent or tomentose. 
Follicles tomentose, covered with soft spinose processes. 
Corona-hoods obtuse, short. 16. A. syriaca. 
Corona-hoods elongated, lanceolate. 17. A. speciosa. 
Follicles with no spinose processes, glabrous or pubescent. 
Leaves wavy-margined ; corolla-segments 4”-5” long. 18, A. arenaria. 
Leaves flat ; corolla-segments 2”—3” long, 19. A. ovalifolia. 
Leaves lanceolate, oblong-lanceolate or linear. 
Leaves opposite, lanceolate or oblong-lanceolate. 
Leaves thick, short-petioled; inflorescence woolly. 20. A. brachystephana, 
Leaves thin, slender-petioled ; inflorescence downy. 21. A. perennis, 
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