118 MISC. PUBLICATION 101, U. S. DEPT. OF AGRICULTURE 
Cactus roughage is extremely succulent and is salty, having a heavy 
mineral (ash) content; unfortunately it has a tendency to sour unless 
fed shortly after preparation. If eaten too freely, moreover, it is 
apt to cause scours. Pricklypears and some other cacti form an im- 
portant part of the food supply and an indispensable source of water 
to jack rabbits, kangaroo rats, and other desert animals. Vernon 
Bailey (6) states that the very abundant Engelmann pricklypear 
(O. engelmannt) (fig. 88, C, D) is the favorite food of jack rabbits 
in Arizona, and he has ascertained that water makes up 78 per cent 
of the weight of its pads. The fruit of many of our pricklypears, 
often known as tunas, is of good quality and valued for human con- 
sumption, some of the species being cultivated for their fruits (56). 
OTHER GENERA 
Ariocarpus (syn. Anhalonium) species have both toxic and 
medicinal properties (95). Mechanical stock poisoning due to hair- 
balls (phyto-bezoars) is not infrequently attributed to cacti, owing 
to ingestion of large quantities of spines and prickles. Cactus is the 
State flower of New Mexico. Giant cactus (Carnegiea gigantea, syn. 
Cereus giganteus), the State flower of Arizona, also known as 
saguaro, has good edible fruits. Arizona water cactus (Hchino- 
cactus wislizent, syn. Ferocactus wislizeni), often called bisnaga or 
viznaga, is an exceedingly important source of water in the desert 
and its fleshy pulp is much used locally in making candy. The 
familiar nightblooming cereus (Hylocereus spp.), commonly culti- 
vated for ornament, is reported by Schneider (718) to be poisonous. 
The notorious peyote (Lophophora williamsii), sometimes called 
mescal, has dangerous narcotic properties (109). The nopal, 
(Nopalea cochenillifera), often called cochineal cactus, is the host 
of the economically valuable cochineal scale insect. Several species 
of cactus, notably queen-of-the-night (Selenicereus grandifiorus, syn. 
Cereus grandifiorus), producing a valuable cardiac stimulant, are 
important medicinal plants. 
SILVERBERRY FAMILY (ELAHAGNACEAE) 
This is almost universally designated in the manuals as the ole- 
aster family. Oleaster, as now understood, belongs to the olive 
family (Oleaceae) and is the genuine wild olive of the Old World 
(Olea oleaster), which some say is the original stock of the cultivated 
common olive (QO. europaea). Something like 20 species of 
Elaeagnus are known, most of them being native to Europe, Asia, 
and Australia. The confusion of this family and the genus Elaeag- 
nus with the true and unrelated olives (Olea spp.) seems to go back 
to the dawn of history. The generic name Elaeagnus signifies 
“sacred olive.” There is some question, however, as to whether or 
not our genus Elaeagnus—gotten from Tournefort and Linnaeus— 
is the Elaeagnus of the ancient Greeks. 
Silverberry (Zlaeagnus commutata, syn. EF. argentea Pursh, not 
Nutt.), often called silverbush and silver birch, the sole American 
representative of its genus, inhabits the far North from northern 
Quebec to Alaska, and south to southeastern British Columbia, 
northern Utah, South Dakota, and Minnesota. It is usually a 
