FOREST FORMATIONS OF THE ISTHMUS OF PANAMA 83 



shouldered man with a small head and a wingless hat. The bark is 

 smooth and reddish and, like the Ceiba and certain Burseraceae, it 

 does not offer a convenient substratum for epiphytic vegetation. 



Several other trees contribute to the formation of the upper story 

 of the monsoon-forests, among them Enterolobium timbouva, which, 

 in opposition to the congenerous Guanacaste, E. cyclocaqium, is a real 

 forest tree; Pentaclethra filamentosa, an elegant Mimosaceous tree; a 

 conspicuous species of the recently described genus Dilodendron, etc. 

 But the following, lower story is exceedingly rich in beautiful types, 

 mostly very much mixed and scattered, bvit also sometimes semi-gre- 

 garious. To be brief, I shall only mention, among the Leguminosae, 

 two species of Centrolobium, two of Pterocarpus, a Peltogyne with 

 beautiful purple wood, Platymiscium polystachium, Platy podium max- 

 onianum, several Dalbergias, among them Dalbergia retusa, the main 

 source of the much discussed cocobola-wood of commerce ; among the 

 Anacardiaceas, Spondias lutea and Anacardium rhinocarpus, which 

 enterprising American firms tried to put on the San Francisco market 

 as mahogany wood, but which proved to be too hard on tools on ac- 

 count of the silica crystals which fill its cells ; several Sapotacese, Bur- 

 seraceae. and Rutaceae, and among the Bignoniaceae, jacaranda and 

 Tecoma guayacan, both with gorgeous blossoms, respectively blue and 

 yellow, and the latter with one of the hardest timbers of the tropics. 



The space under the large trees, which rise to an average height of 

 25 to 30 m., is much more open than in the rain-forest. The epiphytic 

 vegetation is also less developed, but the vines and trailers are more 

 numerous and varied. To be noted, also, is the relative abundance 

 of thorny vines and shrubs, and the presence of cespitose palms with 

 slender stems and elegant bearing. Traveling through this tyj)e of 

 forest is almost everywhere free and easy. 



As we proceed from Panama westward the forest forniaiion becomes 

 more broken and at the same time assumes a more xcrophilous char- 

 acter, without, however, ever assuming, as in the northern districts of 

 Venezuela, the extreme case of an underbrush luixcd with Cereus 

 and Opuntia species. These woods belong to the type designated as 

 savanna-forests and are better considered in connection with the study 

 of the grass formations. At the extreme western end of Panama. 

 the monsoon-forest ajjpears again with a strongly modiiied composi- 

 tion as to its floristic elements, but with the same general characters. 



We know very little as yet as to the change ])niduce(l in the rain- 

 forest of Panama by the increase in altitude and the correspondent 

 depreciation in tem])eraturi'. Tn the deciduous forests of the southern 



