pterocactus. 31 



Key to Species. 



Seeds narrowly winged; spines up to 2 cm. long i. P. hickenii 



Seeds broadly winged; spines 3 to 10 mm. long. 



Joints strongly tuberculate 2 . P. fischeri 



Joints scarcely tuberculate. 



Ovary densely covered with weak spines; wing of seed i mm. wide 3. P. pumilus 



Ovary loosely covered with stiff spines; wing of seed 2 mm. wide 4. P. tuberosus 



Figs. 31, 32. — Pterocactus 

 hickenii. X0.7. 



Fig. 3i-- 



-Pterocactus fischeri. X i . 

 by Paul G. Russell. 



Photograph 



1. Pterocactus hickenii sp. nov. 



Rootstocks moniliform, consisting of at least 4 joints widely separated; joints above ground 

 2 or 3, 2 to 3 cm. long, almost hidden by the spines; spines from each areole numerous, slender, 

 yellow above, brown at base; glochids numerous; fruit and flower not known; seeds thick, 5 mm. in 

 diameter, with narrow lateral wing. 



Collected by Cristobal M. Hicken 

 (No. 3284) January 10, 1914, near Como- 

 doro Rivadavia, southeastern Chubut, 

 Argentina. 



Figures 3 1 and 32 represent a plant 

 and a seed from the specimen above cited 



2. Pterocactus fischeri sp. nov. 



Stems low, i dm. high or less, spreading or erect, cylindric, 1.5 cm. in diameter, tuberculate; 

 leaves minute, acute ; tubercles about as long as broad, arranged in spiral ridges somewhat resembling 

 those of Opuntia wkipplei; spines numerous, the radials 12 or more, white, setaceous, 6 mm. long, 

 spreading; centrals usually 4, i to 1.5 cm. long, brownish, the tips and bases often yellowish; 



Seeds of three species of Pterocactus. 

 Natural size. 



