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STANDLEY TREES AND SHRUBS OF MEXICO. 143 



Stamens 6 ; flowers green. 



Stamens all antheriferous 3. D. pallens. 



Stamens partly (3) reduced to staminodia 4. D. densiflora. 



Stamens 3; flowers purplish 5. D. convolvulacea. 



Staminate flowers about 2 mm. long. Stamens 3. 

 Leaves large, mostly 12 to 18 cm. wide, the basal sinus often closed. 



6. D. grandifolia. 

 Leaves mostly 6 cm. wide or narrower, the basal sinus open. 



7. D. capillaris. 

 Staminate flowers fasciculate or spicate in the racemes. 

 Staminate flowers pubescent. Stamens 6. 



Flowers greenish white 8. D. laxifl.ora. 



Flowers purplish 9. D. dugesii. 



Staminate flowers glabrous. 

 Flowers in short dense spikes, these arranged in racemes. 



10. D. spiculiflora. 

 Flowers fasiculate or in short loose racemes. 



Stamens 3. Flowers 2 to 3 mm. long, greenish white. 



Staminate flowers 3 mm. long 11. D. platycolpota. 



Staminate flowers scarcely more than 2 mm. long__12. D. pringlei. 

 Stamens 6. 



Stamens subequal 13. D. macrostachya. 



Stamens unequal. 

 Flowers purplish, the racemes mostly solitary. 



14. D. composita. 

 Flowers green, the racemes in loose panicles__15. D. floribunda. 



1. Dioscorea alata L. Sp. PI. 1033. 1753. 



Cultivated in Mexico and in some places, as in Oaxaca, apparently natural- 

 ized. Native probably of Asia, but widely cultivated. 



Leaves mostly orbicular-cordate, taper-pointed, glabrous, sometimes very 

 large ; flowers greenish. Known in Mexico as " igname," " iname," or " iiame ; " 

 " nangate " ( Oaxaca ) . 



The large roots of the yam are valuable for human food. 



2. Dioscorea lobata Uline, Bot. Jahrb. Engler 22: 427. 1896. 

 Dioscorea lobata morelosana Uline, Proc. Amer. Acad. 35: 323. 1900. 

 Morelos, Mexico, and Veracruz ; type collected near the City of Mexico. 

 Leaves puberulent, shallowly or deeply lobed. 



3. Dioscorea pallens Schlecht. Linnaea 17: 610. 1843. 

 Veracruz, the type from Jalapa. 



Plants glabrous ; capsule 1.2 to 1.4 cm. long. 



4. Dioscorea densiflora Hemsl. Biol. Centr. Amer. Bot. 3: 356. 1884. 

 Veracruz to Chiapas; type from Valley of Cordoba. Guatemala and Hou- 



dui'as. 

 Glabrous except upon the racemes ; flowers in very long slender spikes. 



5. Dioscorea convolvulacea Schlecht. & Cham. Linnaea 6: 49. 1831. 

 Dioscorea galeottiana Kunth, Enum. PI. 5: 409. 1850. 



Dioscorea co7ivolvulacea viridis Uline, Bot. Jahrb. Engler 22: 427. 1896. 

 Mexico to Michoacftn and Oaxaca. 



Leaves usually puberulent ; flowers long-pedicellate, purplish ; capsules 1.5 to 

 2.5 cm. long. 



D. convolvulacea viridis is a form A\ith 3-lobed leaves. 



6. Dioscorea grandifolia Schlecht. Linnaea 17: 602. 1843. 

 Jalisco to Morelos and Puebla ; type from AcatlSn, Puebla. 



