HOUSE, THE GENUS IPOMOEA 183 



or divided, usually petioled. Flowers solitary on axillary peduncles or in 

 cymes, rarely in raceme-like clusters. Sepals 5, membranaceous or rather 

 fleshy, sometimes becoming leathery, often herbaceous, closely imbricated, 

 sometimes elongated. Corolla funnelform or funnelform-campanulate, 

 rarely salverform, the tube often constricted within the calyx, the limb 

 usually spreading, the plicae ending at the middle of the margin of each 

 lobe, rarely between the lobes. Stamens 5, included, rarely exserted. 

 Ovary 2-, 3-, 4- or rarely 5-celled. Styles united. Capsule mostly septi- 

 fragally 2-, 3-, 4- or 5-valved, sometimes thick-walled and elongated. Seeds 

 glabrous, pubescent or hirsute on the angles, often with a long wool-like 

 coma on the dorsal angles. 



Key to the Sections of Ipomoea. 



Plants erect, stout, perennial, shrubby or tree-like; 



leaf-blades rarely cordate. SECTION I. ORTHIPOMCEA. 



Plants twining, creeping or prostrate, stout or 

 slender; leaf-blades often cordate. 



Sepals herbaceous, often elongated and hairy; 



ovary usually 3-celled. SECTION II. PHARBITIS. 



Sepals coriaceous, membranaceous or sub- 

 herbaceous; rarely elongated; ovary usu- 

 ally 2- or 4-celled. Section III. BATATAS. 



Key to the Subsections. 



I. ORTHIPOMOEA. 



Shrubby below or with stout, erect or ascending herbaceous 

 stems. 



Sepals lanceolate, acuminate; plant silvery. 1. Argyrophyllae. 



Sepals ovate or ovate-oblong, usually obtuse or acute; 



foliage not silvery but often pubescent. 2. Leptophyllae. 



Arborescent, erect and woody. 3. Arborescentes. 



II. PHARBITIS. 



Inflorescence densely capitate or leafy-bracted. 4. Cephalanthae. 



Inflorescence not conspicuously bracted or capitate. 

 Ovary typically 3- or 5-celled. 



Outer sepals becoming different from the inner ones, cor- 

 date or truncate and often conspicuously broadened 

 at the base. 5. Heterophyllse. 



Sepals not becoming cordate or truncate nor conspicu- 

 ously enlarged in fruit. 



