Note 100 — IDEAS FOR A PHYSIOGNOMY OF PLANTS.

p. 229—“The Willow Form.”

Nearly 150 different species of the main representatives of this form, or rather of the Willow itself, are already known. They cover the northern parts of the earth from the equator to Lapland. Their number and their varieties of form increase between the 46th and 70th degrees of latitude, more especially in that part of northern Europe which has been so remarkably indented by the early revolutions of our planet. I am acquainted with ten or twelve species of inter-tropical Willows, and these, like the Willows of the southern hemisphere, are deserving of special attention. As nature appears to delight in all zones in a wondrous multiplication of certain animal forms, as for instance, Anatidæ (Lamellirostres), and Pigeons; so likewise are Willows, Pines, and Oaks, widely diffused; the latter always exhibiting a similarity in their fruit, although various differences exist in the form of the leaves. In Willows belonging to the most widely different climates the similarity of the foliage, of the ramification, and of the whole physiognomical conformation, is almost greater 342than in Coniferæ. In the more southern part of the temperate 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 Forskäl, 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. Wallich’s catalogue of the plants of Nepaul and the Himalaya already gives 13 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. (Thunb.), 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 expedition, 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, probably a mere variety of the former. In like manner the beautiful and frequently pyramidal Willow, which we constantly saw 343on the banks of the Magdalena river, from Mahates to Bojorque, and which, according to the report of the natives, had only spread thus far within a few years, may also be identical with S. Humboldtiana. At the confluence of the Magdalena with the Rio Opon, we found all the islands covered with Willows, many of which had stems 64 feet high, with a diameter of from only 8 to 10 inches.^[QU] Lindley has made us acquainted with a species of Salix belonging to Senegal, and therefore to the equinoctial region of Africa.^[QV] Blume also found two species of Willow near the equator in Java, one wild and indigenous in the island (S. tetrasperma), and another cultivated (S. Sieboldiana). I am only acquainted with the two Willows belonging to the south temperate zone, which have been described by Thunberg (S. hirsuta and S. mucronata). They grow interspersed with Protea argentea, which has the same physiognomy as the Willow, and their leaves and young branches constitute the food of the hippopotamus of the Orange River. The family of Willows is entirely wanting in Australia and the neighbouring islands.