C. H. TYLER TOWNSEND — BIOGEOGRAPHY OF MEXICO, ETC. 
45 
ical forest, the views to he obtained from the mountain sides when the 
trail emerges into an opening are magnificent. 
Not far above Tezuitlan, but much farther above Jalacingo, the road, 
enters an entirely different region. Here the vegetation, the grass, the 
pine trees farther np, even the rocks, the soil and the yellow dnst of the 
road, remind one of the New Mexico monntain regions. The Tropical 
has been left far below, and the Lower Sonoran as well; while the higher 
levels of the Upper Sonoran are everywhere evident, giving way to the 
Transition which is next passed into and traversed. The Upper Sonoran 
mnst begin here at abont 6000 feet, and the Transition mnst. extend 
from abont 8500 or 9000 feet upward. The road goes for long distances 
through pine woods, the air is clear and the sky blue, the birds possess 
the habitus of northern species and remind one of the latter by 
their song — in fact, one can hardly resist the delusion that he is in the 
Transition of New Mexico, and practically it is the same region. From 
here the road descends again somewhat, leaving the pines behind but 
not far above, and emerges upon the Plains of Perote. It is some ten 
miles across these plains, which must be about 8500 feet elevation, or 
possibly a little more. Here the maguey ( Agave americana) grows, ap- 
parently at about its best so fa? as the production of a good quality of 
pulque is concerned, for the pulque of Perote has the reputation of be- 
ing the best in Mexico. It seems that the maguey must be considered, 
in the valleys and plains of the southern table-land region of Mexico, 
to grow in the Upper Sonoran as well as the Lower Sonoran zones, thus 
exceeding here the possibilities of its zonal range in Texas and Northern 
Mexico. This case is perhaps somewhat paralleled by the peculiarities in 
the range of Larrea in California and New Mexico, as mentioned in 
paper I. Possibly, in the case of the maguey, sheltering mountain ridges 
exert some influence in this condition of things; while I believe that the 
Larrea , in California, has adapted itself more to the warmer tempera- 
tures natural to the Pacific coast region, but has been unable on the At- 
lantic slope to invade to any extent the corresponding stretches of 
Lower Sonoran in Mexico. It must be borne in mind that the Atlantic 
slope stretches of the Upper and Lower Sonoran are vastly more extensive 
than those of the Pacific slope; and this fact carries with it a greater 
element of competition among species, not to mention differences in 
soil, humidity, seasonal winds, etc., between these two regions of the 
country. 
TABASCO, CAMPECHE, AND YUCATAN.— In April and Ma y, 
the trip was made from Vera Cruz by coast steamer to Coatzocoalcos, 
Frontera, Laguna, and Campeche; by rail from Campeche to Hecel- 
chakan in Yucatan; bv volan from Hecelchakan to Maxcanu, thirty-six 
