742 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Spines of the fruit retrorsely barbate. 



Petals none; gynophore very sliort, wittiout glands 1. T. lappula. 



Petals present ; gynophore somewhat elongate, with 5 glands at base. 



Upper surface of leaves densely stellate-pubescent 2. T. semitriloba. 



Upper surface of leaves pilose with long, mostly simple hairs. 



3. T. dumetomm. 

 Spines of the fruit glabrous, puberulent, or pilose with long spreading hairs. 

 Calyx 20 to 35 mm. long, or sometimes larger. 

 Petals less than half as long as the sepals and concealed by them. 



4. T. speciosa. 

 Petals nearly as long as the sepals, conspicuous. 



Leaves ovate or broadly rhombic, long-petiolate, broadest at or near 

 the base. 

 Petiole with large glands at apex ; leaves broadly rhombic ; petals 5 to 



6 mm. Avide 5. T. coriacea. 



Petiole without glands ; leaves ovate or lance-ovate ; petals 2 mm. wide. 



Petals densely long-pilose at base 6. T. columnaris. 



Petals very sparsely and minutely stellate-pubescent at base. 



7. T. chihuahuensis. 

 Leaves oblong to rounded-obovate, short-petiolate or sessile, broadest 

 at or above the middle. 

 Sepals with very short thick appendages; leaves minutely stellate- 

 pubescent on the upper surface 8. T. cucullata. 



Sepals with long slender appendages; leaves coarsely stellate-pubes- 

 cent on the upper surface. 



Sepals 2.8 to 3.5 cm. long 9. T. polyandra. 



Sepals 2 cm. long 10. T. obovata. 



Calyx 6 to 18 mm. long. 



Petals none 11. T. apetala. 



Petals present. 



Fruit dehiscent 12. T. dehlscens. 



Fruit (so far as known) indehiscent. 



Appendages of the sepals 3.5 to 5 mm. long 13. T. falcifera. 



Appendages less than 3 mm. long. 



Leaves glabrous, or the pubescence of the upper surface chiefly 

 or wholly of simple hairs. 

 Leaves glabrous except for tufts of hairs beneath in the axils of 



the veins . 14. T. mexicana. 



Leaves pubescent on one or both surfaces. 



Spines nearly or quite as long as the body of the fruit, slender ; 



leaves broadly ovate, slender-cuspidate 15. T. grandiflora. 



Spines very short, stout; leaves ovate-lanceolate, acuminate. 



16. T. g^oldmanii. 

 Leaves copiously stellate-pubescent or tomentose on both surfaces. 

 Petioles short and stout, usually less than 1 cm. long, the upper 

 leaves mostly sessile. 



Upper leaves sessile; stamens usually 15 17. T. palmeri. 



Upper leaves petiolate; stamens 25 to 30 18. T. brevipes. 



Petioles long and slender. 



Sepals glabrous or glabrate 19. T. acracantha. 



Sepals stellate-pilose. 



Spines of the fruit few, much thickened below. 



20. T. socorrensis. 



