Although chiefly tropical, the cactuses have a perpendicular range, which but few other families enjoy. From the low sand-coasts of Peru and Bolivia they ascend through vales and ravines to the highest ridges of the Andes. Magnificent dark-brown Peireskias (the only cactus genus bearing leaves instead of prickles) bloom on the banks of the Lake of Titicaca, 12,700 feet above the level of the sea; and in the bleak Puna,[16] even at the very limits of vegetation, the traveller is astonished at meeting with low bushes of cactuses thickly beset with yellow prickles. [Illustration: CEREUS GIGANTEUS.] What a contrast between these deformities and the delicately feathered mimosas, unrivalled among the loveliest children of Flora in the matchless elegance of their foliage! Our common acacias give but a faint idea of the beauty which these plants attain under the fostering rays of a tropical sun. In most species the branches extend horizontally, or umbrella-shaped, somewhat like those of the Italian pine, and the deep-blue sky shining through the light green foliage, whose delicacy rivals the finest embroidery, has an extremely picturesque effect. Endowed with a wonderful sensibility, many of the mimosas seem, as it were, to have outstepped the bounds of vegetable life, and to rival in acuteness of feeling the coral polyps and the sea anemones of the submarine gardens. [Illustration: MIMOSA.] Large tracts of country in Brazil are almost entirely covered with sensitive plants. The tramp of a horse sets the nearest ones in motion, and, as if by magic, the contraction of the small grey-green leaflets spreads in quivering circles over the field, making one almost believe, with Darwin and Dutrochet, that plants have feeling, or tempting one to exclaim with Wordsworth-- ‘It is my faith, that every flower Enjoys the air it breathes.’ Among the most remarkable forms of tropical vegetation, the creeping plants, bush-ropes, or lianas (cissus, bauhinia, bignonia, banisteria, passiflora), that contribute so largely to the impenetrability of the forests, hold a conspicuous rank. Often three or four bush-ropes, like strands in a cable, join tree to tree, and branch to branch; others, descending from on high, take root as soon as their extremity touches the ground, and appear like shrouds and stays supporting the mainmast of a line-of-battle ship; while others send out parallel, oblique, horizontal, and perpendicular shoots in all directions.