CACTACER, SILVA OF NORTH AMERICA, 17 
OPUNTIA SPINOSIOR. 
Tassajo. 
Joints of the branches green or purple, their tubercles ovate, narrow, full, and 
rounded below the areole; spines white or reddish brown. Flowers pink. Fruit 
yellow, sparingly spinescent, rarely proliferous. 
. Opuntia spinosior, Toumey, Bot. Gazette, xxv. 119 (1898). 
Opuntia Whipplei, 8 spinosior, Engelmann, Proc. Am. 
Acad. iii. 307 (1856) ; Pacific R. R. Rep. iv. pt. v. 51, t. 
17, f. 1-4; Bot. Mex. Bound. Surv. ii. 57.— Hemsley, 
Bot. Biol. Am. Cent. i. 554.— Coulter, Contrib. U. S. 
Nat. Herb. iii. 451. — Schumann, Monog. Cact. 670. 
Opuntia arborescens, Engelmann, Pacific R. R. Rep. iv. 
51, pt. v. t. 17, £5, 6 (not Engelmann, Wislizenus Memoir 
of a Tour to Northern Meaico [Senate Doc. 1848], Bot. 
Appx. 6).— Toumey, Garden and Forest, ix. 2, f. 1. 
A tree, with an erect trunk occasionally ten feet in height and from five to ten inches in diameter, 
and numerous stout vertically spreading branches which fotm an open irregular head. The bark of 
the trunk and of the large limbs is about a quarter of an inch in thickness, spineless, nearly black, 
broken into elongated ridges, and finally much roughened by numerous thin closely appressed scales. 
The joints of the branches are cylindrical, from four to twelve inches in length and from three quarters 
of an inch to an inch in thickness, covered with a thick epidermis which varies in color from green 
to purple, and usually develop woody skeletons during their second season; their tubercles are promi- 
nent, compressed, ovate, and from one third to one half of an inch long, with oval areole clothed with 
pale tomentum and short light brown bristles; their spines, which vary in number from five to fifteen 
on the tubercles of young joints and from thirty to fifty on those of older branches, are slender, from 
white to light reddish brown in color, closely invested in white glistening sheaths, stellate-spreading, and 
from one half to three quarters of an inch in length, those in the interior being sometimes considerably 
longer than the radical spines. The leaves are terete, about a quarter of an inch long, and taper grad- 
The flowers, which 
unfold during April and May, remain open for two or three days, and appear to depend on the visits of 
bees and other insects for fertilization ;* they are from two to two and a half inches in diameter when 
fully expanded, with ovaries about an inch in length, obovate sepals, broadly obovate dark purple petals, 
ually to the setulose apex; they remain on the branches from four to six weeks. 
sensitive red stamens,’ and six to nine-parted stigmas. The yellow fleshy acrid fruits are clustered at 
the ends of the branches of the previous year, and when ripe make them pendulous by their weight; 
they are oval or rarely globose or hemispherical, and frequently two inches long and an inch and a half 
thick, with from twenty to thirty tubercles; during the summer these are very prominent, but as the 
fruits ripen they enlarge and become succulent and the tubercles nearly disappear, leaving the fruits 
marked only by the small oval areole covered with short bristles and armed with numerous slender 
spines, which are deciduous in December as the fruits begin to turn yellow. The seeds vary from one 
fifth to one sixth of an inch in diameter and are nearly orbicular, slightly or not at all beaked, and 
1 «These insects, attracted to the flower, enter between the style minutes the stamens assume their normal condition and the flower 
and stamens, passing down to the base of the style to get the nectar. 
The numerous sensitive stamens immediately bend forward toward 
the style, closing over the insect and hiding it from view. It neces- 
sitates quite an effort on the part of the insect to escape, but it 
finally forces its way from beneath the stamens and climbs to the 
top of the elongated stigma, whence it makes its escape, thoroughly 
dusted with the pollen from the numerous stamens. In a few 
is ready for the reception of other insects. I have frequently seen 
as many as three honeybees inclosed in a single flower.” 
Garden and Forest, ix. 3.) 
2 Professor Toumey points out the facts that the stamens of all 
the Opuntias with cylindrical branches are sensitive, and that when 
disturbed they close tightly round the style a few lines below the 
stigma. (See Bot. Gazette, xxv. 123.) 
(Toumey, 
