496 House: North American Convolvulaceae 



usually enlarged in fruit. Corolla campanulate, campanulate-fun- 

 nelform, or sub-sal verform. Stamens included or protruding, the 

 anthers spirally twisted. Disk hypogynus or obsolete. Ovary 

 2-celled, 4-ovuled. Capsules large, often extremely so, 2-celled 

 and usually 4-seeded, or partially 4-celled, usually differentiated 

 into an upper thicker and a lower thinner portion, or the thin- 

 walled capsule covered by an operculum-like, quatrefoil cap 

 which is deciduous at maturity. More rarely, the capsule of uni- 

 form texture and valved ; the dehiscence transverse or irregular. 

 Seeds large, black or brown and usually smooth. 



Type species : Operculum Convolvulus S. Manso, /. c. {Con- 

 volvulus macrocarpus L., 0. macrocarpa Urban). About 20 spe- 



cies of tropical distribution. 

 Turpithum Raf. Fl. Tellur. , 



71. 1836. 



Spiranthera Boj. Hort. Maurit. 226. 1837. Not Spiranthera 



A. St. Hil. 1823. 

 Piptostegia Reichenb. Nom. 113. 1841. — Hoffmannsegg, in 



Mart. Syst. Mat. Med. Veg. Bras. 78. 1843. 

 I pom oca § Operculum Griseb. Fl. Br. W. Ind. 467. 



1 861. 



Key to tlie Btortli American species 



Leaves entire. 



Stems conspicuously winged. 



Stems glabrous ; corolla yellow, 4-5 cm. long. 1. O. alata. 



Stems pubescent or pilose. 



Corolla white ; peduncles exceeding the subtending 

 petioles. 



Corolla violet ; peduncles shorter than the subtend- 

 ing petioles. 



Stems not winged ; peduncles usually winged. 



Corolla white or cream-colored ; leaf- blades deeply cor- 



2. O. triquetra. 



3. O. leptoptera 



date, 10-30 cm. long. 4. O. ventricosa. 



Corolla not white ; leaf-blades shallowly-cordate, rarely 



more than 10 cm. long. 

 Corolla yellowish ; peduncles obscurely or not at all 

 . winged, 1-2-flowered. 5. O. rhodocalyx. 



Corolla scarlet or salmon-colored ; peduncles con- 

 spicuously winged. 



Corolla scarlet ; peduncles 1-3-flowered. 6. O. rubicunda. 



Corolla salmon-colored ; peduncles flexuose, 2-7- 

 flowered. 



Leaves lobed or divided. 



7. O. alatipes. 



Stems winged ; corolla white. 8. O. macrocarpa 



