STANDLEY TREES AND SHRUBS OF MEXICO. 581 



Hairs of stem fill incurved or appressed. 

 Aril A^eil-like, with broad scarious lobulate margin, covering one-third 

 to three-fifths of seed, the dorsal margin vertically descending, 

 the lower margin nearly or quite horizontal. 



Sepals and wings quickly deciduous 23. P. obscura. 



Sepals and wings subpersistent 24. P. lozani. 



Aril not veil-like. 



Upper leaves ovate to elliptic or lance-oblong. 



Lobes of aril oblong to deltoid ; wings 5 to 5.8 mm. long. 



25. P. parrasana. 

 Lobes of aril linear or lance-linear ; wings 3.5 to 5 mm. long. 



26. P. compacta. 

 Upper leaves linear 27. P. oaxacana. 



II. HEBANTHA. 



Capsule merely ciliate at maturity. 



Hairs of stem all incurved or appressed. 

 Stem subterete ; wings 5.5 to 6.6 mm. long. 

 Stem and leaves .sparsely strigillose ; leaves narrowly lanceolate. 



28. P. longipes. 

 Stem and leaves densely strigillose or incurved-puberulous ; leaves ovate 



to rhombic-lanceolate 29. P. velata. 



Stem strongly angled ; wings 4.5 mm. long 30. P. polyedra. 



Hairs of stem (at least in part) wide-spreading. 



Leaves lanceolate ; wings ciliate 31. P. galeottii. 



Leaves ovate; wings not ciliate 32. P. rivinaefolia. 



Capsule pubescent on sides at maturity. 



Keel 3.2 to 3.5 mm. long; wings 3.8 mm. long 33. P. brachytropis. 



Keel 4.2 to 6.8 mm. long ; wings 4.5 to 7 mm. long. 

 Wings rather densely pubescent over whole outer surface. 



Sepals 4 to 4.5 mm. long; capsule reticulate 34. P. americana. 



Sepals 2.5 to 8 mm. long ; capsule scarcely reticulate— 35. P. pedicellata. 

 Wings sparsely pubescent or puberulous chiefly at apex and base and along 

 costa, or subglabrous. 

 Wings 6.5 to 9 mm. long. 



Hairs of stem partly short and incurved, partly long and spreading. 



41. P. bifonnipilis. 

 Hairs of stem all similar, appressed or incurved-spreading. 

 Capsule spreading-pilosulous ; aril with minute umbo. 



36. P. cuspidulata. 

 Capsule incurved-puberulous ; umbo medium-sized. 



37. P. appressipilis. 

 Wings 4.5 to 5.8 mm. long. 



Wings suborbicular, glabrous except for the ciliolate margin and the 

 finely puberulous costa ; sepals 1 to 2 mm. long. 



38. P. brachysepala. 

 Wings oval, pubescent at least along costa ; sepals 2 to 3.8 mm. lon,T. 



Dorsal margin of aril strongly descending; umbo medium or large 



39. P. raicrotricha. 

 Dorsal margin of aril horizontal or erectish ; umbo minute. 



40. P. chiapensis. 



