342 VIEWS, &iC. PHYSIOGNOMY OF PLANTS. 



than in Coniferse. In the more southern part of the tempe- 

 rate zone, north of the equator, the number of the species of 

 Willows decreases considerably; although (according to the 

 " Flora atlantica" of Desfontaines) Tunis has still its own 

 species, resembling Salix caprea; whilst Egypt, according to 

 Forskal, numbers five species, from the catkins of whose 

 male blossoms is distilled the remedial agent Moie chalaf 

 {aqua salicis), so much used in the East. The Willow which 

 I saw in the Canaries is also, according to Leopold von Buch 

 and Christian Smith, a peculiar species (S. canariensis), although 

 common to those islands and to Madeira. Wallick's cata- 

 logue of the plants of Nepaul and the Himalaya already gives 

 1 3 species belonging to the subtropical zone of the East Indies, 

 and which have in part been described by Don, Roxburgh, 

 and Lindley. Japan has its own species, of which one, S. 

 japonica, (Thumb.), is also met with in Nepaul as an Alpine 

 plant. 



There was not, as far as I am aware, any species of Willow 

 known as belonging to the tropical zone before my expedi- 

 tion, with the exception of S. tetrasperma. We collected 

 seven new species, three of them on the plateaux of Mexico, 

 at an elevation of 8500 feet above the level of the sea. 

 Still higher, as for instance on the Alpine plains, between 

 12,000 and 15,000 feet, which we frequently visited, we saw 

 nothing in the Andes of Mexico, Quito, and Peru, to remind 

 us of the many small creeping Alpine Willows of the 

 Pyrenees, the Alps, or of Lapland (S. herbacea, S. lanata, 

 and S. reticulata). In Spitzbergen, whose meteorological 

 relations have so much analogy with those of the snow- 

 crowned summits of Switzerland and Scandinavia, Martius 

 described two Dwarf- Willows, whose small woody stems and 

 branches trail along the ground, and are so concealed in the 

 turf bogs that it is with difficulty their diminutive leaves can 

 be discovered under the moss. The Willow species which I 

 found in 4° 12' south lat., at the entrance of the Cinchona or 

 Peruvian Bark forests, near Loxa in Peru, and which has 

 been described by Willdenow as Salix Humboldtiana, is most 

 widely diffused over the western part of South America. A 

 Beach- Willow (S.falcata), which we discovered on the sandy 

 shores of the Pacific, near Truxillo, is, according to Kunth, pro- 

 bably a mere variety of the former. In like manner the beauti- 

 ful and frequently pyramidal Willow, which we constantly saw 



