578 



NATURALIST'S GUIDE TO THE AMERICAS 



intermediate zones may be obliterated 



or so intermingled as to become difficult 

 to distinguish. In the high altitudes 

 of this section facing the coast the 

 temperatures are low and suited to the 

 needs of the northern forest and accom- 

 panying fauna, while extreme humidity 

 derived from warm cloud formations 

 prevents frost and favors the upward 

 extension of tropical elements. On the 

 higher parts of certain slopes nearly 

 continuous fog or rain has produced a 

 heavy forest cover, with slow rate of 

 evaporation and slight range of variation 

 in temperature throughout the year. 



1. Major life areas 



The names of plant indicators or 

 botanical features are used for con- 

 venience in designating most of these 

 areas, which it should be understood 

 are each characterized by a great num- 

 ber of species of both animals and plants. 



a. Tropical Zone {including rain for- 

 est and arid tropical deciduous forest). 

 This zone as a whole occupies the low- 

 lands and tropical (normally frostless) 

 slopes of the mountains from 5000 to 

 7000 ft. altitude under favorable local 

 conditions in the southern part of the 

 Republic, the upper limit descending to 

 sea level north of Tampico on the Gulf 

 coast, and to low elevations along the 

 west slope of the Sierra Madre Occi- 

 dental in Sinaloa and southern Lower 

 California. It is divisible into Lower 

 and Upper Tropical sections, and at low 

 elevations into Humid and Arid ele- 

 ments with irregular boundaries, im- 

 perfectly known, and impossible to trace 

 in detail in a short account. The Humid 

 Lower Tropical section is fairly uni- 

 formly covered with an evergreen for- 

 est. The Arid Lower Tropical division 

 includes the coastal plain on the Pacific 

 side north to northern Sinaloa, and 

 parts of the coastal plain in Vera Cruz, 

 Campeche, and Yucatan, together with 

 some of the interior valleys of southern 

 Mexico. Owing to the long dry winter 

 season much of the forest is deciduous. 

 Along the Pacific coast within this arid 

 belt sections of forest alternate with 



sections of grass-land or savanna some- 

 what mixed with an irregular growth of 

 Ciiratella, Coccoloba, Byrsonima, and 

 other trees of non-forest types. The 

 Tropical Zone as a whole, includes the 

 vast fauna and flora which pushes north- 

 ward from Central America, and is 

 divided into eastern and western 

 branches near the Isthmus of Tehuante- 

 pec by the southward thrust of the 

 central highlands. 



The habitats of the plants and ani- 

 mals are not well enough known to 

 locate them in plant areas. E. — east- 

 ern, largely rain forest; S. — southern, 

 largely rain forest; W. — western, largely 

 arid tropical deciduous forest. See 

 map. 



Plants 



Dicranopteris bancroftii, fern. E. 

 Dicranopteris Hexuosa, fern. E. 

 Dicranopteris pectinata, fern. E. 

 Dicranopteris bifida, fern. E. 

 Dicranopteris palmata, fern. E. 

 Cyathea princeps, tree fern. E. 

 Cyathea mexicana, tree fern. S. 

 Hemitelia costaricensis, tree fern. S. 

 Alsophila quadripinnata, tree fern. S. 

 Pinus pringlei, Pringle's pine. W. 

 Pinus oocarpa, ocote. VV, 

 Zamia spartea, cycad. S.E. 

 A canthorriza mocinni, palma de escoba. 



S. 

 Chamaedorea elegans, palm. E. 

 Attalea cohune, corozo. S. 

 Acrocomia mexicana, coyol. W. and S. 

 Agave ixtli, ixtle. S.E. 

 Ficus padifolia, wild fig. Ranges 



widely. 

 Brosium alicastrum, ramon. Ranges 



widely. 

 Castilla elastica, rubber tree, hule or 



arbol del hule. W. and S. 

 Cecropia mexicana, Guarumo. Ranges 



widely. 

 Coccoloba schiedeana, Tamulero. Ranges 



widely. 

 Talauma inexicana, flor de corazon. S. 

 Annona glabra, li&Xo de corcho. Ranges 



widely. 

 Per sea schiedeana, chinini. E. 

 Capparis Jlexuosa, Ranges widely. 

 Licania arborea, cacahuananche. W. 

 Hirtella americana, cajetillo. W. and S. 

 Leucaena glauca, lead tree. S. 

 Lysiloma acapulcensis, tepehuaje. 



Ranges widely. 

 Inga spuria, jinicuile. Ranges widely. 

 Cassia occidentalis, habilla. Ranges 



widely. 



