148 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Petioles short, usually 4 to 6 mm. long. 

 Leaf blades acute at the base. 

 Leaves 7 to 8 cm. wide, not bullate, thin. 

 Fruit hirsute ; leaves acute-acuminate. 



40. P. descourtilsianum.. 

 Fruit glabrous ; leaves subobtuse-acuminate. 

 I 41. P. colipanum. 



Leaves about 4 cm. wide, somewhat bullate, rigid. 



43. P. misantlense. 

 Leaf blades cordate to obtuse at the base. 

 Leaves glabrous and smooth on the upper surface. 



Leaf blades obtuse at the base 43. P. citrifolium. 



Leaf blades cordate or semicordate at the base. 

 Leaves about 14 cm. long and 6.5 cm. wide. 



44. P. decipiens. 

 Leaves about 23 cm. long and 14 cm. wide. 



45. P. liebmannii. 

 Leaves scabrous on the upper surface. 

 Leaves conspicuously bullate, the pubescence of the lower 

 surface appressed. 

 Leaf blades elliptic-lanceolate, 6 to 11 cm. wide. 



46. P. hispidum. 

 Leaf blades oblong-lanceolate, about 4.5 cm. wide. 



47. P. mexicanum. 

 Leaves not bullate, the pubescence not appressed. 

 Leaf blades tomentose beneath, about 4 cm. wide. 



48. P. leucophyllum. 

 Leaf blades hirtellous beneath, 5.5 to 6 cm. wide. 



49. P. angustifolium. 



Subgenus 6. E^'CKEA. 



Ultimate nerves of the leaves conspicuously transverse-parallel. 

 Leaves hirtellous beneath, linear-acuminate at the apex. 



50. P. melastomoides. 

 Leaves glabrous beneath, acuminate or short-acuminate at the apex. 



Leaves rigid, the upper ones obtuse or acutish at the base ; petioles about 



1.5 cm. long 57. P. smilacifolium. 



Leaves membranaceous, cordate at the base ; petioles 2 to 4 cm. long. 



52. P. marginatum. 

 Ultimate nerves not conspicuously transverse-parallel. 

 Leaves pubescent on both surfaces. 



Petioles 15 to 30 mm. long ; leaves deeply cordate at the base. 



53. P. decrescens. 

 Petioles 2 to 6 mm. long; leaves rounded or shallowly cordate at the base. 



54. P. kunthii. 

 Leaves glabrous on the upper surface, glabrous or pubescent beneath. 



Leaf blades broadly rounded-ovate, glabrous 55. P. jaliscanum. 



Leaf blades ovate or narrower. 



Leaves 6 to 10 cm. long, 2.5 to 4 cm. wide. 

 Petioles 5 mm. long; leaves puberulent beneath along the nerves. 



56. P. lindenii. 

 Petioles 8 mm. long; leaves glabrous 57. P. unguiculatum. 



