122 CONTRIBUTIONS TO WESTERN BOTANY 
* pe longer than wide, 
Tub _ 8 2-3 times as long as wide. 
3 erect, sheaths 2 mm, wide. 
anches clustered at a of stems, joints 
‘int readily falling, fruit very spinuse above 
and bare below and dry. 4 echinocarpa. 
Branches not clustered above, racemose, 
— readily falling and swollen in 
iddle, flowers red and proliferous. 6 prolifera 
Sane as or arcuate below 
stems elongated and prostrate, flowers 
greenish-yellow, 6 serpentina 
Stems not over 6 inches long, arcuate, 
with tip erect, spines flattened and 
sheathless, flowers yellow. 7 clavata 
Tubercles linear and elongated, at least 
4 times as long as wide, fruit dry, stems erect, 
pect Seto fruit not biennial, 
spin 8 acanthocarps. 
ewer vain fruit hh spinose 
around the upper margin 9 Parryi 
Platyopuntia. 
Fruit dry. 
Fruit about eight seeds large. 10 basilaris 
Fruit spinos 
Areoles about 4 inch apart, spines 
air-li 11 ursina. 
Areoles % 3 “acheg apart, usnally 
spineless belo 12 rhodantha 
Fruit edible and juicy. 
Stems with trunk, erect, very yellow | 
spined, frnit purple, with green juice. 13 chlorotica 
Stems prostrate or spreading widely. 
Stems ii spreading, the base 
rarely er 14 occidentalis 
Stems prostrate or nearly so and forming 
oink fhm mostly he Meo spines 
declineb and white 15 Mohavensis. 
Joints relatively venalk aay in 
a string. 16 Vaseyi. 
