978 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Stigma lobes red. 



Plants globose or somewhat elongate 56. N. haageana. 



Plants depressed-globose 57. N. perbella. 



Stigma lobes white. 



Radial spines appressed 58. N. collina. 



Eadial spines not appressed - 59. N. donatii. 



Radial spines brownish when young, stouter 60. N. mundtii. 



Central spines usually 4, sometimes more. 

 Central spines white or yellow. 

 Radial spines white. 

 Plants globose. 



Axils of tubercles not setose ; central spines usually 4, rarely 



as many as 7 61. N. celsiana. 



Axils of tubercles setose ; central spines usually 9. 



62. N. aureiceps. 



Plants cylindric 63. N. yucatanensis. 



Radial spines yellow. 



Plants globular 64. N. pringlei. 



Plants slender-cylindtric 65. N. cerralboa. 



Central spines brown or black. 



Central spines black 66. N. phaeacantha. 



Central spines brown. 



Axils of tubercles not setose 67. N. graessneriana. 



Axils of tubercles setose. 

 Tubercles closely set. 



Central spines not very different from the radial. 

 Plant body more or less elongate; spines brownish or 



reddish 68. N. spinosissima. 



Plant body globose; radial spines whitish. 



69. N". densispina. 

 Central spines very different from the radial. 



70. N. nunezii. 

 Tubercles spreading. 



Central spines unequal ; stigma lobes green. 



71. N. amoena. 

 Central spines nearly equal ; stigma lobes rose-colored. 



72. N. rhodantha. 

 B. Seeds black. Neither tubercles nor stems milky. 



Spines plumose 73. N. plumosa. 



Spines not plumose. 



Radial spines weak and hairlike 74. N. multiceps. 



Radial spines not hairlike. 

 Spines yellow. 



Spines 2 to 8, glabrous, more or less twisted or bent. 



75. N. camptotricha. 



Spines about 20, pubescent, straight 76. N. eriacantha. 



Spines not yellow. 

 Spines 25 to 80. 



Spines pubescent or lanate. 



Spines lanate, 25 to 30 77. N. schiedeana. 



Spines pubescent or puberulent 78. N. lasiacantha. 



Spines not pubescent. 



