110 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



BBB. Leaves rather fibrous, oblong, over 1 mm. long. 



Leaves rather thin and .straight-margined 52. A. lurida. 



Leaves fleshier. 



Margin nearly straight 53. A. rasconensis. 



Margin concave between the teeth 54. A. vera-cruz. 



BBBB. Leaves fleshy, obovate, deeply repand, short. 

 Spine flexuous ; leaves scarcely 25 cm. long. 



Spine and teeth dull rusty brown 55. A. verchafEeltii. 



Spine and teeth gray, gray-brown, or red-chestnut. 



Spine and teeth gray-brown or gray 56. A. megalacantha. 



Spine and teeth red-chestnut 57. A. gnadalajarana. 



Spine straight; leaves twice as long 58. A. potatorum. 



BBBBB. Leaves rather fleshy and long, oblanceolate, repand; teeth very 

 unequal. 

 Spine and teeth red-brown. 



Leaves green 59. A. mescal. 



Leaves grayish 60. A. fenzliana. 



Spine and teeth copper-colored 61. A. cupreata. 



BBBBBB. Leaves fleshy, large, the teeth mostly subequal. 



Leaves green-and-gray-banded, rough 111. A. marmorata. 



Leaves not markedly zoned. 



Spine conical, somewhat recurved. 

 Leaves not sharply reflexed. 



Leaves abruptly acute, plicate 112. A. abrupta. 



Leaves not plicate. 



Spine gradually tapered 113. A. wercklei. 



Spine rapidly very acute 114. A. expansa. 



Leaves reflexed toward the end 115. A. americana. 



Spine needle-shaped. 



Leaves reflexed 116. A. picta. 



Leaves not sharply reflexed. 



Leaves rough 117. A. asperrima. 



Leaves smooth. 



Spine nearly straight 118. A. palmeri. 



Spine flexuous 119. A. flexispina. 



AA. Leaves with the teeth usually joined by a firmly attached horny border. 

 Spine sinuous, rather slender. 



Filaments inserted in middle of tube 62. A. shawii. 



Filaments inserted above the middle 63. A. orcuttiana. 



Spine straight. 



Teeth gradually tapered 64. A. sebastiana. 



Teeth abrupt from a broad base. 



Leaves abruptly acuminate 65. A. pachyacantlia. 



Leaves gradually acute 66. A. g'oldmaniana. 



AAA. Leaves mostly with long-decurrent spine, but scarcely horny-margined 

 between the teeth. 

 H. Leaves oblong, long (over 1 meter). 



Leaves green or subglaucous ; perianth segments long (3 cm.) 



12. A. long^isepala. 



Leaves white-glaucous; segments much shorter 67. A. applanata. 



HH. Leaves ovate or obovate, scarcely half as long. 

 Leaves rather thin ; spine slender. 



Leaves acute, dull gr.ny 68. A. scabra. 



Leaves acuminate, glaucous 70. A. parrasana. 



