24 ASCLEPIADACEAE. VOL. 111. 



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 ? 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. i. 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 i-2-awned. 4. Gonolobus. 



Corolla rotate. 



Anthers tipped with a scarious membrane ; pollen-masses pendulous. 5. Cynanchum. 



Anthers merely tipped ; pollen-masses horizontal. 6. Vincetoxiciim. 



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 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 s-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 syrlaca L. 



* Corolla and corona orange; leaves alternate or opposite. 



Stem erect or ascending ; leaves nearly all alternate. i. 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. 3. A. lanceolata. 



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



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



Flowers 2" -3" broad ; corona-hoods i" i J4" high. 



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



Plant pubescent ; leaves oblong. 7. 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. 



Leaves cordate-clasping. 10. A. amplexicaulis. 



Leaves rounded at the base, short-petioled. n. 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. J7 A.speciosa. 



Follicles with no spinose processes, glabrous or pubescent. 



Leaves wavy-margined; corolla-segments 4"-s" long. 18. A.arenaria. 



Leaves flat; corolla-segments 2" -3" long. 19- A.ovahfolia. 



Leaves lanceolate, oblong-lanceolate or linear. 



Leaves opposite, lanceolate or oblong-lanceolate. 



Leaves thick, short-petioled; inflorescence woolly. 20. A. brachy Stephana. 



Leaves thin, slender-petioled ; inflorescence downy. 21. A.pcrennis. 



