STANDLEY TREES AND SHRUBS OF MEXICO. 357 



BB. Stamens twice as many as the corolla lobes. 



Branches more or less bristly-hispid, usually armed with spines also, In 

 one species the pubescence only obscurely hispid, but the spines then 

 tipped with flexuous bristles. 



Stems bristly but without spines 36. M. camporum. 



Stems armed with spines. 



Rachis of the leaf bristly but without spines; pinnae 20 to 25 pairs. 



37. M. galeottii. 

 Rachis of the leaf armed with spines. 



Bristles of the peduncles usually gland-tipped ; corolla striate. 



38. M. somnians. 

 Bristles of the peduncles eglandular ; corolla not striate. 



Pods obovate, 1 to 3-seeded ; spines with slender flexuous tips. 



39. M. dormiens. 

 Pods linear-oblong, 15 to 20-seeded ; spines stiff, straight. 



40. M. pigra. 

 Branches not bristly-hispid ; spines never ending in flexuous bristles. 

 C. Corolla glabrous. 



Fruit winged ; peduncles rufous-tomentose. Leaflets 2 to 3 mm. wide. 



41. M. hemiendyta. 

 Fruit not winged ; peduncles not rufous-tomentose. 

 Leaflets 3 to 17 mm. wide or broader. 



Plants unarmed; leaflets coriaceous, 6 to 17 mm. wide. 



43. M. leucaenoides. 

 Plants armed with spines ; leaflets thin, mostly 3 to 8 mm. wide. 

 Leaflets glabrous. 



Pinnae one pair ; leaflets about 8 pairs 44. M. m.iclieliana. 



Pinnae 3 or 4 pairs ; leaflets 4 or 5 pairs 53. M. wootonii. 



Leaflets pubescent. Pinnae 3 or more pairs. 



Leaflets rhombic, acute or acutish, mostly 5 to 8 mm. wide, 

 soft-pilose beneath when young; branches pilose. 



45. M. ervendbergii. 

 Leaflets oblong, rounded at the apex, 3 to 4 mm. wide, mi- 

 nutely strigillose ; branches puberulent or glabrate. 



46. M. argillotropha. 

 Leaflets 2 mm. wide or narrower. 



Pinnae 1 to 3 pairs ; leaflets few, usually 5 pairs or fewer. 



Spines geminate 47. M. tenuiflora. 



Spines solitary 58. M. lindheimeri. 



Pinnae 3 to many pairs ; leaflets numerous. 



Petioles equaling or longer than the rachis, densely armed with 



short recurved spines 48. M. invisa. 



Petioles much shorter than the rachis, unarmed or with a few 

 scattered spines. 

 Leaflets 8 pairs or fewer ; fruit about 6 mm. wide. 



49. M. grahami. 

 Leaflets 20 to 32 pairs, thin ; fruit often 2 cm. wide. 



Pinnae 6 to 12 pairs 50. M. eurycarpa. 



Pinnae 15 to 18 pairs 51. M. colimensis. 



CC, Corolla pubescent, at least on the lobes. 



Leaflets 4 to 6 mm. wide 52. M. malacophylla. 



Leaflets less than 3 mm. wide. 



Fruit with 2 broad lacerate wings 42. M. lacerata. 



Fruit not wihged. 



