56 
EXPLANATION OF THE PLATES. 
showing the thickness and hairy spines, upper younger joints (unfinished); 2, hunch of spines 
from a younger joint; 3, same from an older part of the plant; 4, fruit. 
Fig. 5-7. Opuntia hystricina, E. & B.: 5, a joint (unfinished); 6, a large bunch of spines ; 
7, fruit. 
Pl. XVI. Opuntia Davisii, E. & B.: 1, a branch showing the structure of the older parts, 
an older and young joints with two fruits ; 2, a tubercle with its hunch of spines, the membran¬ 
aceous sheaths partly torn, showing the spine itself; 3, a degenerate sterile spiny fruit in its 
transition to a branch, as it is often seen in this species and others, especially cylindric opuntia; 
4, the whole plant reduced. 
Pl. XYII, Fig. 1-4. Opuntia Whipplei, E. & B. : 1, a branch of the more common form of 
the plant covered with ripe fruit. At (a) the fruit is undeveloped, probably not different from 
the ovary of the flower, only more shrivelled ; 2, branch of a larger specimen, spines more 
numerous, fruit larger ; 3, a single hunch of spines of this specimen ; 4, whole plant reduced. 
Fig. 5-6. Opuntia arborescens, E. : 5, a stout branch with numerous spines and large fruit; 
6, a hunch of spines of same. 
Pl. XYIII, Fig. 1-3. Opuntia acantiiocarpa, E. & B.: 1, an older branch with fruit; 2, a 
young branch ; 3, whole plant reduced. 
Fig. 4. Opuntia arborescens, E. : whole plant reduced. 
Fig. 5-10. Opuntia echinocarpa, E. & B. : 5, a branch of the plant densely covered with the 
sheathed spines ; 6, 7, and 8, hunches of spines ; 9, fruit, side view ; 10, same, top view. 
Pl. XIX. Opuntia Bigelovii, E. : 1, a single joint; 2 and 3, tubercles, with hunches of 
spines ; 4, young undeveloped fruit; 5, an apparently full-grown fruit, sterile, and perhaps 
degenerating into a branch ; 6, part of the ligneous skeleton, forming a wide tube, and showing 
in the reticulated structure the traces of the tubercles and branches ; 7, an entire plant reduced ; 
on the left of the main stem is a younger shoot, with vigorous erect joints. 
Pl. XX, Opuntia vaginata, E. : 1, an older joint bearing two fruits, and a young vigorous 
shoot. 
Fig. 2-3. Opuntia frutescens, E., var. longispina : from Williams’ river of the Colorado ; 2, 
a branch with fruit; 3, lower part of the trunk, with some roots ; the sections show the struc¬ 
ture of the dense wood. 
Fig. 4-5. Opuntia frutescens, E., var. brevispina : 4, a branch with fruits, most of them 
sterile, one producing young branches from its upper areola; 5, a flower. 
Pl. XXI. Opuntia tesselata, E. : 1, a branch with fruit a, a, and a withered flower b; 2 
and 3, flowers as they probably are reconstructed from withered specimens ; 4, a small joint 
magnified so as to show distinctly the appearance of the tubercles and areolm ; 5, part of the 
stem with a section of the wood above and a fracture below, so as plainly to show the ligneous 
structure ; the hark of the younger branches exhibits the tesselated surface, while in the older 
trunk it is lost in the irregular scales ; 6, ligneous skeleton of a young branch ; 7, a whole 
plant reduced. 
Pl. XXII, Fig. 1-3. Opuntia clavata, E: 1, joint with a ripe fruit; 2, one of the upper 
bunches of spines ; 3, part of the central spine magnified 4 diameters. 
Fig. 4-7. Opuntia Parryi, E : 4, joint with ripe fruit; 5, hunch of spines, side view ; 6, another 
one, front view ; 7, part of the central spine magnified 4 diameters. 
The remaining figures of this and all the two following plates represent seeds and then- 
details of almost all the Opuntia described in this report. Fig. a represents a side view of the 
seed, natural size ; b, same, four times magnified, as are all the following figures ; c, posterior 
view; d, anterior view ; e, vertical section of seed, exhibiting the position and proportion of 
the embryo and the albumen ; f, embryo and albumen coated by the endopleura, after the 
removal of the testa ; g , lateral view of embryo. The other letters h, i, 1c, etc., will be explained 
wherever they occur. 
