446 CONTRIBUTIONS FROM THE NATIONAL, HERBARIUM. 



Calyx not strongly angled, conspicuously glandular. 

 Leaflets pubescent on the upper surface; racemes lax. Petals 



purplish 19. P. schaffneri. 



Leaflets glabrous on both surfaces; racemes dense. 



Petals, except the banner, purplish 20. P. hegewischiana. 



Petals all greenish yellow 21. P. viridiflora. 



Calyx glabrous within. 

 Calyx lobes equaling the tube. 



Branches strlgose 22. P. oculata. 



Branches glabrous. 



Kacemes short, at the ends of short leafy branches. 



23. P. crenulata. 

 Kacemes 8 to 12 cm. long, on naked peduncles opposite the 



leaves 24, P. elongata. 



Calyx lobes much shorter than the tube. 



Leaf rachis distinctly winged, constricted at the nodes. 



25. P. nutans. 

 Leaf rachis not winged but slightly margined. 



Racemes headlike or subumbellate 26. P. gracillima. 



Racemes elongate, not headlike. 



Racemes 2 to 5-flowered, lax 27. P. diffusa. 



Racemes many-flowered, dense. 



Racemes 1 to 2 cm. long ; plants decumbent. 



28. P. dispansa. 

 Racemes 3 to 8 cm. long; plants erect_-29. P. submontana. 

 AA. Flowers sessile, ascending. 



B. Calyx lobes subulate-tipped, usually longer than the tube. 



Spikes subsessile at the ends of short axillary branches as well as at the 

 ends of the main branches. 

 Leaves and branches glabrous or nearly so, except when very young. 

 Spikes short but not capitate, mostly short-pedunculate or at the ends 



of short leafy branches 30. P. scandens. 



Spikes capitate, sessile in the leaf axils and at the ends of the branches. 



Leaflets 11 or 13, 3 to 4 mm. long 31. P. capitulata. 



Leaflets 5 to 9, 4 to 11 mm. long 32. P. tehuacana. 



Leaves and branches conspicuously villous. 



Calyx without conspicuous glands between the ribs 65. P. sessilis. 



Calyx with conspicuous glands between the ribs. 

 Bracts ovate, acute, scarcely longer than the calyx tube. 

 Spikes, at least in fruit, lax ; leaf rachis evidently winged. 



33. P. domingensis. 



Spikes short and dense ; rachis scarcely winged 34. P. humilis. 



Bracts lance-ovate, long-acuminate, much exceeding the calyx tube. 



35. P. occidentalis. 

 Spikes terminating the stem and branches. 

 C. Petals yellow, fading to rose or purplish. 



Calyx not conspicuously gland-dotted between the ribs ; leaves glabrous. 



Calyx tube glabrous 42. P. argyrostachya. 



Calyx tul)e pubescent. 



Leaflets 7 to 11, often einarginate, blackening in drying. 



36. P. melantha. 

 Leaflets 11 to 35, not eniarginate, not blackening. 

 Leaflets 2 to 6 mm. long; corolla less than 1 cm. long. 



37. P. zimapanica. 



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