STANDLEY TEEES AND SHRUBS OF MEXICO. . 1203 



3. Exogonium velutifolium House, Bull. Torrey Club 35: 100. 1908. 

 Type from west side of Valley of Cuicatlan, Oaxaca. 



Leaves short-petiolate, oblong-ovate, 1 to 3 cm. long, obtuse, densely pubescent ; 

 bracts linear-lanceolate ; corolla crimson, 3 cm. long, glabrous. 



4. Exogonium argentifolium (A. Rich.) House, Bull. Torrey Club 35: 102. 



1908. 



Ipomoea argentifolia A. Rich, in Sagra, Hist. Cuba 11: 131. 1850. 



Puebla and Oaxaca. Cuba ; type from Isle of Pines. 



Leaves petiolate, oblong-lanceolate to elliptic-oblong, 2 to 10 cm. long, acute 

 or obtuse, acute or rounded at base, whitish-tomentose or finally glabrate; 

 cymes many-flowered ; corolla about 4.5 cm. long. 



5. Exogonium conzattii (Greenm.) House, Bull. Torrey Club 35: 102. 1908. 

 Ipomoea consattii Greenm. Field Mus. Bot. 2: 258. 1907. 



Guerrero and Oaxaca ; type from Almoloyas, Guerrero. 



Cymes many-flowered, the pedicels white-tomentose ; sepals tinged with red, 

 obtuse ; corolla about 3 cm. long. 



7. IPOMOEA L. Sp. PI. 159. 1753. 



Reference : House, The North American species of the genus Ipomoea, Ann. 

 N. Y. Acad. Sci. 18: 181-263. 1908. 



Plants erect or scandent, usually herbaceous but sometimes woody; leaves 

 entire, dentate, or lobate, sometimes digitately compound ; flowers solitary, 

 racemose, or cymose ; sepals membranaceous or herbaceous ; corolla usually 

 funnelfoi-m, the limb spreading; stamens included; ovary 2 to 5-celled. 



Numerous herbaceous species of the genus occur in Mexico. The best-known 

 representative of the genus is the sweet-potato ("camote"), Ipomoea batatas 

 (L.) Lam., which is widely cultivated in Mexico. Other species, known as 

 " morning-glories," or in Spanish as " campanula," are often grown as orna- 

 mental vines because of their beautiful flowers. 



Plants erect, stout ; leaves usually not cordate at base. 

 Plants large shrubs or trees ; leaves entire. 



Corolla pink or purple; seeds densely black-hairy 1. I. crassicaulis. 



Corolla white ; seeds white-hairy only on the angles. 



Corolla and sepals densely lanate outside 2. I. murucoides. 



Corolla and sepals glabrous or pubescent, not lanate. 



Leaves densely pubescent beneath, with prominent venation. 



Leaves mostly ovate, cordate at base 3. I. arborescens. 



Leaves mostly lance-oblong, rounded at base 4. I. cuernavacensis. 



Leaves glabrous beneath or nearly so, the venation not prominent. 



Sepals hairy within, 12 to 16 mm. long 5. L intrapilosa. 



Sepals glabrous within, 8 to 12 mm. long. 



Leaves mostly 7 to 13 cm. long 6. I. wolcottiana. 



Leaves 2 to 4 cm. long 7. I. calva. 



Plants low, 30 to 60 cm. high, fruticose only at base; leaves often trilobate. 



8. I. ciervensis. 

 Plant scandent; leaves usually cordate at base. 



Sepals herbaceous, often elongate ; ovary usually 3-celled. 

 Inflorescence capitate or leafy-bracted. 

 Stems minutely pubescent or tomentose. 



Leaves silvery-sericeous beneath ; stems tomentose 9. I. maireti. 



Leaves glabrate beneath; stems nearly glabrous 10. L invicta. 



