STANDLEY TREES AND SHEUBS OF MEXICO. 1015 



Bractlets none. Calyx 4 to 14 mm. long. 



Two dorsal petals larger than the others 1. P. racemosa. 



Two dorsal petals smaller than the others. 



The 9 ventral stamens alternately unequal, 5 of them often subexserted. 



Disk cuplike, investing the base of the ovary 2. P. gaumeri. 



Disk large and investing part of the ovary base, interrupted dorsally. 



3. P. ciliata. 

 The 9 ventral stamens not alternately unequal, included. 



Disk cupuliforra 4. P. utriculosa. 



Disk dorsal 5. P. salicifolia. 



Bractlets present on the pedicel, sometimes very small. 

 Calyx 3 to 11 mm. long ; ovules 2 to 32. 



Flowers opposite 6. P. epilobiifolia. 



Flowers alternate. 



Stamens in anthesis nearly or quite as long as the calyx. 



7. P. hyssopifolia. 



Stamens much shorter than the calyx 8. P. calophylla. 



Calyx 12 to 40 mm. long or, if smaller, bialate within dorsally or the 

 dorsal lobe produced ; ovules sometimes as many as 50. 

 Calyx evidently bialate within, 10 to 24 mm. long, the spur usually sub- 

 ascending, rarely incurved. 

 Two interior wings of the calyx retrorse-hairy ; petals 2. 



Petals about 10 mm. long, dark purple ; spur of calyx incurved. 



9. P. nitidula. 

 Petals 2 to 3.5 mm. long, violet-black ; spur straight or subascend- 



ing 10. P. cyanea. 



Two interior wings of calyx glabrous; petals usually (\, rarely 2. 



Pedicels axillary; petioles up to 17 mm. long 11. P. nudicostata. 



Pedicels interpetiolar ; petioles less than 12 mm. long. 



Leaves 10 to 12 mm. long, glabrous on the upper surface. 



12. P. empetrifolia. 

 Leaves mostly more than 2 cm. long, usually scabrous or pubescent 

 on the upper surface. 

 Ventral petals about half as long as the 2 dorsal ones. 



13. P. pinetoriun. 

 Ventral petals 3 mm. long or less, or absent, much less than half 



as long as the dorsal petals. 

 Flowers not in distinct racemes, the pedicels interpetiolar. 



14. P. chiapensis. 

 Flowers in distinct racemes. 



Kfanches glandular-hirsute; petioles 1 to 2 ram. long. 



15. P. Ixodes. 



Branches retrorse-scabrous or puberulent, glandular-hirtellous 



only in the inflorescence ; petioles usually S to 12 mm. 



long 16. P. hookeriana. 



Calyx not bialate within, sometimes slightly bicostate. 



Dorsal lobe of the calyx large, produced ; calyx usually violet or purplish, 

 never scarlet. Petals usually 6. 

 Scales absent below the petals. 



Petals 2 17. P. llavea. 



Petals 6. 



Calyx 25 to 28 mm. long 18. P. blepharophylla. 



Calyx 15 to 20 mm. long. 



Calyx hirsute with eglandular hairs 19. P. bilimekii. 



Calyx minutely glandular-hirtellous 20. P. goldmanii. 



