68 



THE CACTACEAE. 



Key to Species — continued. 



Radial spines yellow. 



Plants globular 72. A^. pringlei 



Plants slender-cylindric 73. A'', cerralboa 



FF. Central spines brown or black. 



Central spines black 74. N. phaeacantha 



Central spines brown. 



Axils of tubercles not setose 75. N. graessneriana 



Axils of tubercles setose. 

 Tubercles closely set. 



Central spines not very different from radial. 



Plant bodj- elongated; spines brownish or reddish. .. . 76. A'^. spinosissiina 



Plant body globose; radial spines whitish 77. N. densispina 



Central spines very different from the radial 78. N. nunezii 



Tubercles spreading. 



Central spines unequal; stigma-lobes green 79. A^ amoena 



Central spines nearly equal ; stigma-lobes rose-colored . . . 80. N. rhodanlha 

 BB. Seeds black; neither tubercles nor stems milk3' (81-104). 



C. Spines plumose 81. A', plumosa 



CC. Spines not plumose. 



D. Radial spines weak and hair-like. 



Central spines with j-ellow tips 82. N. prolifera 



Central spines with brown tips 83. N. multiceps 



DD. Radial spines not hair-like. 

 E. Spines yellow. 



Spines 2 to 8, glabrous, more or less twisted or bent 84. N. camptolricha 



Spines about 20, pubescent, straight 85. N. eriacantha 



EE. Spines not yellow. 

 F. Spines 25 to 80. 



Spines pubescent or lanate. 



Spines lanate, 25 to 30 86. N. schiedeana 



Spines pubescent or puberulent 87. A^ lasiacaiitha 



Spines not pubescent. 



Spines all very much alike. 



Perianth-segments obtuse 88. N. denudata 



Perianth-segments pointed. 



Flowers about 7 mm. long 89. N. le?ita 



Flowers about 2 cm. long go. N. Candida 



Central spines i to 6, very unlike others 91. N. vetula 



FF. Spines 20 or fewer but sometimes more in N. oliviae and N. potlsii. 

 Plant globose. 



Flowers red 92. N. fertilis 



Flowers white. 



Central spines solitary; radials 7 to 9 93. N. decipiens 



Central spines 5 to 8; radials 16 to 20 94. N. discolor 



Plant cylindric. 



Joints very fragile, breaking loose when touched or jarred. 95. N.fragilis 

 Joints not fragile. 



Spines all radial, recur\'ed, sometimes with one central. . 96. N. elongala 

 Spines both radial and central. 



Plants globose to short-cj'lindric 97. N. oliviae 



Plants slender-cylindric. 



Axils of tubercles not bristly. 



Spines all yellow 98. A'^. echinaria 



Spines not yellow. 



Upper central spines more or less connivent 



over top of plant 99. A^ potlsii 



Upper central spines not connivent 100. N. mazatlanensis 



Axils of tubercles bristly. 



Stems slender-cylindric; central Mexican species. . loi. N. sphacelala 

 Stems short-cylindric or globose (sometimesglobose 

 in N. palmeri) ; Lower Californian species. 

 Spines nearly white or at least becoming so ; seeds 

 minute. 

 Spines all white or nearly so; spine-areoles at 



first lanate 102. N. albicans 



• Spines tan with dark tips; spine-areoles not 



lanate 103. A', slevinii 



Spines not white; seeds 3 mm. long 104. A', palmeri 



AA. Some of central spines hooked; radial spines never hooked (105-149). 

 B. Tubercles milky; seeds brown. 



Plants globose 105. A', uncinata 



Plants cylindric 106. A", hamata 



BB. Tubercles not milky except sometimes in N. rekoi; seeds mostly black. 

 C. Seeds brown. 



Fruit red; flowers from side of plant 107. A^ rekoi 



Fruit green; flowers from near base of plant 108. N. solisii 



