68 THE CACTACEAE. 
KeEy To SPECIES—continued. 
Radial spines yellow. 
Plants globular ....... 0... eee cee eee tree eee eee 72. N. pringlet 
Plants slender-cylindric. 2.0.6... . 0. eee e cee eee eee eee eee 73. N. cerralboa 
FF. Central spines brown or black. 
Central spines black. ........ 0... cece eee eee ee eee ee 74. N. phaeacantha 
Central spines brown. ; 
Axils of tubercles not setose......... 0... eee cece eee eens 75. N. graessneriana 
Axils of tubercles setose. 
Tubercles closely set. 
Central spines not very different from radial. 
Plant body elongated; spines brownish or reddish.... 76. N. spinostssima 
Plant body. globose; radial spines whitish............ 77. N. densispina 
Central spines very different from the radial........... 78. N. nuneztt 
Tubercles spreading. 
Central spines unequal; stigma-lobes green............. 79. N. amoena 
Central spines nearly equal; stigma-lobes rose-colored... 80. N. rhodantha 
BB. Seeds black; neither tubercles nor stems milky (81-104). 
C. Spines plumose.... 1... 0... ec eee eee eee ete ence eee 81. N. plumosa 
CC. Spines not plumose. @ 
D. Radial spines weak and hair-like. 
Central spines with yellow tips........ 0.0... cece eee ee eee eens 82. N. prolifera 
Central spines with brown tips................ eee eee eect ees 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. camptotricha 
Spines about 20, pubescent, straight............ 0.0... 0c cece eee 85. N. ertacantha 
EE. Spines not yellow. 
F. Spines 25 to 80. 
Spines pubescent or lanate. 
Spines lanate, 25 tO 30...... 0... cece cece cence eens 86. N. schiedeana 
Spines pubescent or puberulent......................05. 87. N. lasiacantha 
Spines not pubescent. 
Spines all very much alike. 
Perianth-segments obtuse............ 0.0.0 cece eee ees 88. N. denudata 
Perianth-segments pointed. 
Flowers about 7 mm. long.................00000 00: 89. N. lenta 
Flowers about 2 cm. long.................000 0000s go. N. candida 
Central spines 1 to 6, very unlike others................. gi. N. vetula 
FF. Spines 20 or fewer but sometimes more in N. oliviae and N. pottsit. 
Plant globose. 
Flowers red... .. cee eee ee eee eee eeeenes 92. N. fertilis 
Flowers white. 
Central spines solitary; radials 7 tog. ................ 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, recurved, sometimes with one central.. 96. N. elongata 
Spines both radial and central. 
Plants globose to short-cylindric.................... 97. N. oliviae 
Plants slender-cylindric. 
Axils of tubercles not bristly. 
Spines all yellow... 0... 2.0... cee eee eee 98. N. echinaria 
Spines not yellow. 
Upper central spines more or less connivent 
over top of plant....................... 99. N. pottsit 
Upper central spines not connivent............ 100. N. mazatlanensts 
Axils of tubercles bristly. 
Stems slender-cylindric; central Mexican species... ror. 
Stems short-cylindric or globose (sometimes globose 
in N. palmert); Lower Californian species. 
Spines nearly white or at least becoming so; seeds 
. Sphacelata 
minute. 
Spines all white or nearly so; spine-areoles at 
first lanate....................222-+.-. 102. N. albicans 
Spines tan with dark tips; spine-areoles not 
Janate 2.0... cece ec cece een eens 103. N. slevinit 
Spines not white; seeds 3 mm. long............ 104. N. palmert 
AA. Some of central spines hooked; radial spines never hooked (105-149). 
B. Tubercles milky; seeds brown. 
Plants globose........000000 00. c ccc ccc ec cee cece ce neeeeeuneeeeennnnes 105. N. uncinata 
Plants cylindric. 20.0.0... cece cece cece cece ee ceeeveveveues 106. N. hamata 
BB. Tubercles not milky except sometimes in N. rekoi; seeds mostly black. 
C. Seeds brown. 
Fruit red; flowers from side of plant.............. 0. ccc ceecccccccccecce 107. N. rekot 
. N. solisat 
