360 The Botanical Gazette. [August, 
In a recent observation on Opuntia chlorotica growing at 
Steins Pass, N. M., detached joints were found, at least two 
rods from the plant upon which they grew. They were all 
firmly anchored by long roots penetrating the ground from 
under side of the joint. 
It is with the cylindrical opuntias, however, that the 
spines have an important part to play in vegetal dissemina- 
tion. Nearly all of this large group depend almost entirely 
for dissemination upon the readiness with which the terminal 
branches break off and upon the highly developed barbed 
spines which cover them. : 
One of the species best adapted for dissemination is Opuntia 
Bigelovit, a plant abundant on the mountains and foot-hills 
of south-central Arizona. The tubercles are crowded and the 
pulvilli are covered with numerous, radiating, highly barbed 
spines. These formidable spines are so numerous that 
they completely hide the epidermis of the plant. Although 
the joints are from two to five inches long and more than an 
inch in diameter, the point of union with the old stem is very 
slight, the scar left at the place of detachment being but 
two or three lines in diameter. The slightest touch will de- 
tach the young joints and they cling as formidable burrs to 
any object with which they come in contact. It is not an 
unusual sight on the Arizona plains, to see cattle with scores 
of these burrs firmly fastened to their legs and head. They 
are sometimes carried for miles and when finally detached, 
even after weeks of travel, are in condition to grow. This 
plant depends so completely upon this method of dissemina- 
tion that it has almost entirely lost the power of seed-pro- 
duction. In fifty fruits examined last fall, but two perfect 
seeds were found. Forty-eight of the fruits were sterile and 
the other two had but one perfect seed in each 
Of the fourteen species of Cylindropuntia which I have €*- 
elovit, O. fulgida, O. mamillata, O. echinocarpa and f 
prolifera, are exceptionally well adapted for this method a 
dissemination; the joints are easily detached and are wel 
seldom sterile but the s 
climate, seldom germinate. Among the thousands of spec! 
