196 BOTANICAL GAZETTE [SEPTEMBER 
Opuntia camanchica.—This is the common prickly pear of the 
mesa and arroyos. The specimen shown in fig. 26 occurred in the 
Dysodia-Ephedra association in gravelly sand with small boulders. 
The plant had been formed vegetatively from a fallen segment 
which had become buried. The roots had originated from the 
pulvini and the proximal 2 inches of each was tuberous. The root 
system conforms to the usual superficial type described by CANNON 
for the smaller cacti, except for the presence of one thick, deeply 
* placed root. The plant is usually several joints in height, so that 
Fic. 25- Ak tt +f ‘of Opuntia arborescens, } + tal extension 
-_ -— 
_ joint. The asic tah the thicke ,m placed d root may a 
