The Mexican 

 Sierras 



The East and West Sierras Madre 



and Coastal Plains, and the Sierra del Sur 



I From scholarly students to humble farmers of the mountains, 

 Mexicans are exceptionally alert to the physical nature of their 

 country. Almost any wayfarer in country districts can tell you 

 just what kind of bosque (vegetation) is to be found where, what 

 kind of trees and flowers grow in said bosque, and so forth. 

 Similarly, visits to agricultural and forestry departments of uni- 

 versities and state bureaus are a pleasure for biologists and espe- 

 cially phytogeographers. because one almost invariably meets 

 therein enthusiasts of all kinds, working busily at their local 

 problems and integrating their findings with an over-all picture. 

 It is a rather sad commentary, therefore, that the excellent tech- 

 nical reports of this work are rarely translated into English, let 

 alone made readily available outside Mexico. I mention this 

 because 1 have nowhere else encountered such a volume of 

 published information on the subject that interests me most, 

 while no natural province on this continent is less known popu- 

 larly than the one now to be described. 



Tourists and other foreign visitors stream in and out of Mexico 

 from north, south, east, and now even from the west, but they 

 all do so either by air or along a limited number of roads and 

 railways. If you study a good up-to-date road map of northern 

 Mexico, you will find that only one road crosses the western 

 slice of that country and one the East Sierra — the first from 

 Torreon via Durango to Mazatlan; the second from Huisache via 

 Ciudad del Mais to Mante (see map). Of course, at the bottom 

 of the plateau where the two Sierras Madre converge and abut 

 onto the volcanic Sierra del Sur. there is a great network of 

 roads, which lace this latter range also, but the main bodies of 

 the two grandest parts of the province are quite untapped. I have 

 penetrated these vast areas at a number of points over the last 

 twenty years, mostly in the earlier days on the west side on foot 

 or on horseback but more recently by automobile into the eastern 

 Sierras, and what 1 have seen therein has never ceased to amaze 

 me. I am therefore astonished at the continued absence of pub- 

 lished non-tedinical information on these areas, or even of any 

 mention of them in general works. 



All but the outer fringes of the two great Sierra complexes are 

 truly hidden lands. Their very existence is not apparent to people 



Mighty Popocatepetl and its mate Ixtaccihuatl.the dominant 

 volcanic peaks of the Sierra del Sur. a range that cuts off 

 the bottom of the continent. 



passing along the normal routes of travel. The fo<ithilU. and even 

 the outer ranges of these two tremendous mountain complexes or 

 both their inner (facing the plateau) and outer (facing the coasts) 

 sides are generally arid, while along those limited southern 

 stretdjes. where they come right down to those coasts, they rise 

 so precipitously that travel into them is extremely difficult The 

 roads snake their way through them by means of the lowest 

 possible passes or along river valleys which are almost nowhere 

 even forested. Unless otherwise informed, nobody driving south 

 on any of the four main roads — the Pacific coast road; the El 

 Paso-Chihuahua— Durango; the Laredo— Monterrey-San Luis Po- 

 losi: and the Brownsville— Ciudad Victoria— Tama/unchale routes 

 — would ever suspect that within a comparatively few miles to 

 one side of them lie valleys choked with a tropical type of vege- 

 tation, over which parrots and other splendidly colored birds 

 squawk and yell and where glorious waterfalls splash and 

 rumble. Here, cycads and fabulous palms drip in the mists, the 

 branches of the greater trees are loaded with orchids and brome- 

 liads and other epiphytes, and. among other exotica, a great 

 chasm, many times larger than our own Grand Canyon, lies 

 waiting to be properly explored. 



Nor. indeed, would even the more adventurous travelers have 

 any conception of the vast oak forests and open pine forests, with 

 a continuous carpet of grass beneath the trees, that sprawl in an 

 immense U-shaped belt around this province from the Arizona 

 border south to the twentieth parallel; thence, right across the 

 country to the east; and then north again, to within sight of Big 

 Bend in Texas. These oak forests are almost as little known as 

 the "jungles" or Iropicales of the inner valleys. They have no 

 roads; but. instead, little meandering pony trails lead to many 

 still quite aboriginal Amerindian villages. What is more, the 

 traveler is often paced along these paths for lengthy periods by 

 inquisitive but discreet wolves. Here, in the upper highlands, 

 one enters a world the existence of which is never suspected by 

 the average North American and which, be it admitted, is seldom 

 visited even by any Mexicans other than local inhabitants. 



North America tapers down at its base to a narrow isthmus 

 that curves off to the southeast and then straight east. It is vir- 

 tually pinched off at the Isthmus of Tehuantepec. a gutter that 

 runs due north to south, that does not rise above 850 feet, and 

 that separates the massive mountains of northern Mexico from 

 the uplands of Chiapas and Central America. At the outset of 

 our journey we decided to make the crest of the great volcanic 

 range of mountains, sometimes known as the Sierra Madre del 

 Sur. which crosses Mexico from east lowest at about the twentieth 

 north parallel, the base of our continent. In the last chapter we 

 approached this line within half a degree down the central up- 

 land plateau that extends south from the deserts of Chihuahua. 

 Previously, in the Sonoran and in the East Chaparral provinces, 

 we ranged south across the deserts and hot scrublands on both 

 the west and east sides of the country to the edge of the sub- 

 tropics. There thus remains to be visited this large cup- or V- 

 shaped block of mountainous territory, lying between these three 

 prongs of dry hot lands This is in many respects one of the most 

 interesting provinces on this continent, and certainly the most 

 varied and exotic. 



Despite its great extent, its wide spread in both latitude and 

 longitude, and its tremendous variations in altitude, it has a 

 certain unity. This is most apparent in the field we are partic- 

 ularly interested in— namely, the distribution of various types 

 of vegetation, their manner of growth, and their order of suc- 

 cession. The exoticism and the excitement in visiting these lands 

 are supplied by the tropical influences, which are, to the inhabit- 

 ants of temperate latitudes, as bizarre as those of polar regions. 



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