In strong contrast with the extreme flexibility and fresh, light-colored verdure of the climbing plants, of which we have just been speaking, are the rigid, self-supporting growth and bluish hue of the form of the Aloes, which, instead of plaint stems and branches of enormous length, are either without stems altogether or have branchless stems. The leaves, which are succulent, thick, and fleshy, and terminate in long points, radiate from a centre and form a closely crowded tuft. The tall-stemmed aloes are not found in close clusters or thickets like other social or gregarious plants or trees; they stand singly in arid plains, and impart thereby to the tropical regions in which they are found a peculiar, melancholy, and I would almost venture to call it, African character. Taking for our guides resemblance in physiognomy, and influence on the impression produced by the landscape, we place together under the head of the Aloe form (from among the Bromeliaceæ), the Pitcairnias, which in the chain of the Andes grow out of clefts in the rocks; the great Pourretia pyramidata (the Atschupalla of the elevated plains of New Granada); the American Aloe (Agave); Bromelia aranas and Bromelia karatas; from among the Euphorbiaceæ the rare species which have thick, short candelabra-like divided stems; from the family of Asphodeleæ the African Aloe and the Dragon tree (Dracæna draco); and lastly, from among the Liliaceæ, the tall, flowering Yucca. If the Aloe form is characterized by an almost mournful repose and immobility, the form of Gramineæ, especially the physiognomy of arborescent grasses, is characterized, on the contrary, by an expression of cheerfulness and of airy grace and tremulous lightness, combined with lofty stature. Both in the East and West Indies groves of bamboo form shaded overarching walks or avenues. The smooth, polished and often lightly waving and bending stems of these tropical grasses are taller than our alders and oaks. The form of Gramineæ begins even in Italy, in the Arundo donax, to rise from the ground and to determine by height as well as mass the natural character and aspect of the country.