Books and Current Literature 



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flat-stemmed Opuntia, tree-like Pereskia, and the tall, cande- 

 labra-shaped Cereus eburneus, together with arborescent acacias, 

 various species of Crot'on, and other Ivuphorbiaceae. On the 

 hills beyond there are great stretches of Agave and Aloe, in 

 places trees with leathery leaves, and among these an under- 

 growth including various bromeliads. A few epiphytes, in- 

 cluding Rhipsalis, certain Polypodiaceae, etc., also occur. In 

 the valleys, under cultivation, are groves of coconut, mango, 

 sapodilla, and orange trees, which afford a good place for the 

 growth of annual plants. The trees of the forests which clothe 

 the mountain sides from 300 meters upward include Bombax, 

 Clusia, Cecropia, the palms Acrocomia, Oreodoxa, and Bactris, 

 and a variety of other woody plants which become dwarfed as 

 the summit is approached. At lower levels there is a thin under- 

 growth of ferns and orchids, which becomes thicker at higher 

 altitudes, including besides these Dioscorea, Smilax, Piper, 

 Philodendron, Anthurium, and other characteristic genera, with 

 a few grasses, and in wet places Cyperus, Scirpus, Eleocharis, 

 and a few other Cyperaceae. Thus, the distribution of plants 

 upon the island is seen to be definitely correlated with the great 

 variety of vegetative conditions determined by its geographical 

 position and physical features. 



The distribution of individual species, whether in groups 

 or singly, in one place or scattered in many, and whether on one 

 slope and not on another, presents an interesting field for 

 study. As to the question why certain plants are found on one 

 slope and not on another, the palms are taken as an example. 

 At an altitude of 500 meters or niore, palms of various kinds are 

 scattered about among the other forest vegetation. This occurs, 

 however, only on slopes to the northeast, that is, exposed to the 

 northeast trades The opposite sides at this high altitude pre- 

 sent an ordinary forest-front undotted by a single palm. Mois- 

 ture, then, either by its immediate presence, or in its relation to 

 the winds, very probably is here a controlling factor. 



The distribution of plants on the island according to season 

 is quite as impressive a phenomenon as their distribution in the 

 various topographical regions. In the rainy periods the fields 

 are carpeted with green and the bushes and trees are heavy with 

 foliage and bright with flowers. In the dry season the fields are 



