16 SILVA OF NORTH AMERICA. CACTACEA, 
secondary fruits are frequently sterile ; it is dull green when fully ripe, with dry flesh, and falls usually 
during the first winter, although occasionally a fruit remains on the branches during a second season 
and develops flowers from its tubercles ; the fruit is oval, rounded, and from an inch to an inch and a 
quarter in length, nearly as broad as it is long, more or less tuberculate,! conspicuously marked with 
large pale tomentose areole bearing numerous small bristles and, although usually spineless, occa- 
sionally small weak spines. The seeds are compressed, thin, very angular, and from one twelfth to one 
sixth of an inch in diameter.? 
Opuntia fulgida, which is a plant of the plains, and is not rare in Arizona south of the Colorado 
plateau and in the adjacent region of Sonora, apparently is most abundant and grows to its largest 
size on the mesas near Tucson, at elevations between two thousand and three thousand feet above the 
level of the sea. It is said to grow also at Cottonwood Springs in southern Nevada and at Calamuget, 
and on Magdalena Island in Lower California. 
The wood of old trunks, which contains a thick pith, is light, hard, and pale yellow, with broad 
conspicuous medullary rays and well marked layers of annual growth.’ 
This Cactus, the Vera de Coyote of the Mexican Indians, was first made known to science by the 
botanists attached to the commission which defined the boundary between the United States and 
Mexico. It is one of the most conspicuous and interesting plants of the mesas of southern Arizona, 
where in the clear atmosphere of the desert the lustrous sheaths inclosing its numerous spines glistening 
in the sunlight make it visible for many miles. 
1 The depth of the tubercles on many of the cylindrical Opun- 
tias, especially on the mature or nearly mature fruit, depends 
almost entirely on the amount of moisture. During exceedingly 
dry seasons the tubercles are deep and the fruit small and 
shriveled. On the same plants during a moist season the fruit is 
large and plump, and the tubercles are scarcely raised above the 
remainder of the surface. This is true, only not to so great a 
degree, of the younger branches of the plant itself. (Toumey, in 
litt.) 
? Onthe foothills of the mountain ranges of southern Arizona and 
northern Sonora a form of this plant occurs with thicker shorter 
joints, more prominent but shorter tubercles, and fewer spines, 
usually only from four to six spines being developed from the tuber- 
eles of the terminal joints, although from those of older joints as 
many as twenty or thirty are produced. The flowers and fruit of 
the two forms appear to be identical, but the foothill variety is a 
smaller plant than that of the mesas. It is: — 
Opuntia fulgida mamillata, Coulter, Contrib. U. S. Nat. Herb. 
iii. 449 (1896). — Toumey, Bot. Gazette, xxv. 121. 
Opuntia mamillata, Engelmann, Proc. Am. Acad. iii. 308 
(1856); Bot. Mex. Bound. Surv. ii. 58, t. 75, £. 19; Brewer & 
Watson Bot. Cal. i. 250.— Walpers, Ann. v. 57.— Hemsley, 
Bot. Biol. Am. Cent. i. 552.— Toumey, Garden and Forest, viii. 
325. 
8 The log specimen in the Jesup Collection of North American 
Woods in the American Museum of Natural History, New York, 
cut by Professor Toumey in the neighborhood of Tucson, is seven 
inches in diameter inside the bark, with fourteen layers of annual 
growth in the solid exterior layer of wood, which is about two and 
a half inches in thickness. 
EXPLANATION OF THE PLATE. 
Prats DCCVI. 
See er eS 
A seed, enlarged. 
OPUNTIA FULGIDA. 
A flower, natural size. 
Vertical section of a flower, natural size. 
End of a fruiting branch, natural size. 
Vertical section of a fruit, natural size. 
A fruit laid open transversely, natural size. 
A seed showing raphe, enlarged. 
Cross section of a seed, enlarged. 
An embryo, enlarged. 
