v.] REMARKABLE LEAVES. 71 
full-grown specimens of this species have arrived at 
the venerable age of several hundreds of years. Dr. 
Engelmann says: “‘ These trees in abundance give the 
landscape a very peculiar appearance. As far as the 
eye can reach in the valleys or on the mountains, 
little else but rocky boulders and the stately, yet 
awfully sombre, aspect of the 
Cereus giganteus can be seen. 
Some species of Cereus creep 
along the ground instead of 
assuming an erect position. Of 
this kind is the beautiful Cereus 
MacDonaldi@, which flowers 
only at night. It has a bright 
orange calyx, and the deli- 
cate white petals, when fully 
expanded, measure fourteen 
inches across. This species is 
found in Honduras; another and commoner species 
(C. grandiflorus) grows in the West Indies, 
Belonging to the same class of plants and inhabit- 
ing the same locality as the last, we have the well- 
known Prickly Pears (Opuntia), so frequently culti- 
vated in English windows. There are upwards of a 
hundred and fifty species of them, all confined to the 
hot dry districts of America and the West Indies. 
Brazil, Chili, Peru, and Mexico are their headquarters, 
but they have been successfully introduced and well 
established in parts of Europe and Africa. It produces 
its orange-coloured flowers from the flattened joints 
of its stem. They are succeeded by the thick fleshy, 
pear-shaped fruits known as prickly pears. These 
Fic. 77. 
