Cactaceæ in the Galapagos Islands

Abstract

IN my notice (NATURE, p. 623) of Dr. Baur's botanical collections from the Galapagos Islands, I intended to add a few words respecting the Cactaceæ, but forgot it at the last moment. This natural order of plants forms the most conspicuous feature in the vegetation of some of the islands, as may be seen in the excellent views illustrating the cruise of the U.S. ship Albatross; yet Darwin, so far as I can discover, is the only naturalist who ever brought away any specimens, or contributed to any more exact knowledge than can be got from photographs on a very small scale. The presence and abundance of Cactaceæ in these islands is highly interesting, especially in relation to the age and origin of the flora, and to the fact that none exist in Juan Fernandez, though they abound in Chili. They are also of great importance to the animal kingdom during long droughts, as they are then the only source of water. As we learn from Darwin, the succulent branches are eagerly devoured by the large tortoises, lizards, and various other animals. He found that lizards four feet in length were easily enticed whenever he threw them a piece of a branch, and small birds would come within a few feet of him and peck at one end whilst a lizard was eating at the other.1 Darwin also regarded the Cactaceæ as a source of food; and it is noteworthy that animals were mainly dependent on the branches broken off by wind. Opuntia galapageia was found by Darwin on James's Island, growing from six to ten feet high, with a trunk a foot in diameter, and so densely covered with strong spines as to be protected from destruction by predatory animals. The younger branches bear only long elastic bristles. Dr. N. J. Andersson, a Swedish botanist, who visited the islands in 1851, states (Eugenies Resa, “Botanik,” p. 95) that this cactus grows in all the islands, and he adds that he observed at least four or five other species, but had not time to collect specimens or to sketch them. In another place (“Linnæa,” xxxi., 1861–2, pp. 571–631) he particularly mentions the Opuntia growing in lava where nothing else would grow, forming huge candelabra-like objects with pretty red, shining fruits. It is evident, too, from the photographic views reproduced in the “General Sketch of the Expedition of the Albatross” that one (or more) species of Cereus attains a height of ten or twelve feet, and is equally prominent in the landscape. Perhaps the next botanist who visits the islands may find time to study the Cactaceæ. But when will any Government think it of sufficient importance to attach a really qualified botanist to such expeditions? I ought to add that Dr. Baur is not a botanist, but he appears to have done his best as a botanical collector.