18 SILVA. OF NORTH AMERICA. CACTACER, 
marked with linear conspicuous commissures. The fruits remain on the branches during the winter 
and occasionally during the following summer, and then sometimes become proliferous, bearing flowers 
and fruits.’ 
Opuntia spinosior is widely scattered over the mesas of southern Arizona south of the Colorado 
plateau and over the adjacent region of Sonora. : 
The wood of Opuntia spinosior is light, soft, pale reddish brown, and conspicuously reticulated 
with inconspicuous medullary rays and well-defined layers of annual growth.’ It is sometimes used in 
the manufacture of light furniture, canes, picture-frames, and other small articles. 
Opuntia spinosior was discovered in Sonora in 1855 by Mr. A. Schott.’ 
1 Professor Toumey recognizes as var. Neo-Mexicana (Bot. Ga- 2 The log specimen in the Jesup Collection of North American 
zette, xxv. 119 [1898]) a variety of this species which grows with Woods in the American Museum of Natural History, New York, is 
the ordinary form to the same size but is distinguished from it by five and a half inches in diameter inside the bark, with seventy- 
longer tubercles, more numerous spines with looser sheaths, flow- two layers of annual growth in the outer woody portion, which is 
ers with more numerous and much narrower petals varying in color two and one sixteenth inches in thickness. 
from red. to yellow, and larger fruits often more or less tinged with 8 See x. 18. 
ted. 
EXPLANATION OF THE PLATE. 
Prate DCCVII. Opuntia sPrnosior. 
. A flower, natural size. 
- Vertical section of a flower, natural size. 
. The end of a fruiting branch, natural size. 
. Vertical section of a fruit, natural size. 
. A fruit divided transversely, enlarged. 
aoPPwnre 
. A seed, enlarged. 
. A seed showing the raphe, enlarged. 
Vertical section of a seed, enlarged. 
oon 
. An embryo, enlarged. 
