EXPLANATIONS OF THE PLATES OF CACTACEjE. 
Pl. I. Echinocactus Whipplei, E. & B. : fig. 1, whole plant; fig. 2, hunch of spines of the 
usual size ; fig. 3, same, uncommonly large and broad ; fig. 4, same, lateral view ; fig. 5, same, 
very young ; fig. 6, seed— a natural size, b magnified 8 diameters, c part of the surface still 
more magnified to exhibit the tuberculated appearance. 
Pl. II, Fig. 1-2. Echinocactus polyancistrus, E. & B.: 1, upper part of a rib with older 
and younger hunches of spines, the youngest one with a flower hud in the axil; 2, one of the 
largest and most fully developed hunches of spines. 
Fig. 3-5. Echinocactus Le Contei, E. : 3, part of a rih, with 2 hunches of spines ; 4, a single 
hunch of spines from another specimen ; 5, seed— a natural size, b magnified 8 diameters, c part 
of the surface still more magnified to exhibit the oval pits. 
Pl. Ill, Fig. 1-2. Echinocactus Wislizeni, E.: 1, side view of a hunch of spines ; 2, seed— a 
natural size, b magnified 8 diameters, c part of the surface still more magnified to exhibit the 
reticulation. This species, collected by Captain Whipple on the Gila, and common about El 
Paso, on the Rio Grande, has been introduced here to show those characteristics which distin¬ 
guish it from the nearly allied E. Le Contei , on the foregoing plate. 
Fig. 3. Echinocactus Emoryi, E. : two hunches of spines on part of a rih. 
Fig. 4-6. Echinocactus polycephalus, E. & B.: 4, part of a rih, with 3 hunches of short, 
stout, and straightish spines ; 5, a young hunch of spines of unusual dimensions and much 
curved, with a woolly fruit in the axil; 6, seed— a natural size, b magnified 8 diameters, c part 
of the surface more magnified to show the warty appearance, d seed after the removal of the 
outer integument, embryo, together with a considerable quantity of albumen in the endopleura, 
e embryo curved with accumhent cotyledons. 
Pl. IY, Fig. 1-3. Cereus pnasNiCEUS, E.: 1, upper part of a head hearing a flower; 2, a 
hunch of spines of the usual size ; 3, part of a rib, with 3 hunches of spines from an uncommonly 
large form. 
Fig. 4-5. Cereus phceniceus, sub. sp. conoideus, E. & B.: 4, upper part of a head; 5, part of 
a rib, with 2 hunches of spines. 
Fig. 6-7. Cereus triglochidiatus, E.: 6, upper part of a large head, with a flower ; 7, part 
of a rih of another specimen, with smaller curved spines. 
Fig. 8. Cereus Mojavensis, E. & B.: part of a rib, with 3 hunches of spines. 
Fig. 9. Cereus Mojavensis, E. & B., var. zuniensis: part of a rib, with 2 bunches of spines. 
Pl. Y, Fig. 1. Cereus hex^drus, E. & B.: upper part of a head. 
Fig. 2-3. Cereus gonacanthus, E. & B. : 2, part of a rib, with two hunches of spines ; 3, 
another fascicle of spines ; the 3 hunches of spines show all a different proportion of the central 
and the upper radial spines. 
Fig. 4-7. Cereus Engelmanni, var. variegatus, E. & B.: 4 and 5, two hunches of spines, 
showing a different arrangement of central spines ; 6, fruit; 7, seed— a natural size, b magnified 
8 diameters, c part of the surface still more magnified to show the irregular tuherculation. 
Fig. 8-10. Cereus Engelmanni, var. chrysocentrus, E. & B. : 8, part of two ribs, with 
numerous spines ; 9, a single hunch of spines ; 10, fruit, sterile and perhaps not fully developed. 
Pl. VI, Fig. 1-3. Opuntia chlorotica, E. & B.: 1, joint with a flower. The flower to he 
reconstructed from a withered specimen collected in January ; 2, sterile and probably unde- 
