GEOGRAPHICAL BOTANY. 397 



luxuriant growth of the plants, in the vicinity of the 

 Garua, only lasts for a short period. Of the characteristic 

 tropical forms, some are absent, or rarely found; as 

 Epiphytes, all the Monocotyledons, and the Ferns. North 

 of Guayaquil the desert tracts again recur, in which the 

 coast-stream at Salango (2 S. lat.) clothes a spot of land, 

 like an island, with tropical trees ; but as soon as the 

 equator is passed northwards on this coast the vegetation 

 acquires variety and strength. The Orchidaceae and 

 other Epiphytes then become more common ; the number 

 of forest forms rapidly increases in the same proportion 

 as the duration of the rainy season augments, as far as the 

 Bay of Choco (3 7 N. lat.), where the vegetation of the 

 western coast is most copiously developed ; but the solstitial 

 point is also reached at the same time. In this climate, 

 the boundary of which is on this side of the equator, but 

 which is still equatorial, the western coast contains its 

 only Tree-ferns, and even here the Cacti, the characteristic 

 plants of the trade- wind flora of America, are absent. 

 At Panama (9 N. lat.) we again find a proportionate 

 change of the two tropical seasons, hence no Tree-ferns 

 nor Scitamineae are met with there, but arborescent Cacti 

 and other succulent plants. Most of the new species of 

 the collection described by Bentham are from this south 

 region of the western trade- wind coast (9N.lat.to3S. lat.) 

 North of Panama the influx of Mexican types is percep- 

 tible; Heliantheae become numerous ; the forests of maho- 

 gany at Realejo are also succeeded above by a region of 

 Pinus occidentalis, and the oak is found even 15 00' above 

 Acapulco. 654 species of the rich collection have already 

 been described in the parts at present published, which 

 extend from the Polypetalae to the Scrophulariaceae. 

 Families containing most species: Capparidaceae (10), 

 Malvaceae (31), Byttneriaceae (11), Sapindaceae (12), 

 Leguminosae (125), Melastomaceae (23), Rubiaceae (39), 

 Synantheraceae (95), Apocynaceae (13), Bignoniaceae (17), 

 Convolvulaceae (39), Boraginaceae (23), Solaneae (25), 

 and Scrophulariaceae (at present 17). Considering the 



