649 
4. Eastern Sierra Madre Region. 
This forms a narrow strip running along the eastern edge ofthe Mexican 
tableland extending north of Monterey to the Rio Grande, before reaching 
which the chain of mountains becomes less distinct and at last identic with the 
mountains of the tableland. From Presidio on the Rio Grande, the botanist sees 
a lofty mountain (Sierra Rica, 9,000 feet) in the southeast in the state of 
Chihuahua. Its summit is covered with Pinus cembroides and its slopes with 
Quercus undulata (= O.grisea) and Arbutus xalapensis. Three miles below 
Eagle Pass, according to HAVARD (loc. cit.), the banks of the Rio Escondido, 
a clear, swift stream, on the Mexican side is shaded with Carya olivaeformis 
(= Hicoria pecan), Morus celtidifolia, Celtis occidentalis over which clim 
Vitis candicans. On the bluffs above are groves of Ouercus virginiana (= O. 
virens) extending along the hill tops into the interior of Coahuila. 
For some two hundred miles of its extent the Sierra Madre Oriental is 
included within the Mexican state of Nuevo Leon and a sketch of the flora 
of the mountains in this territory will to great extent, in lack of more complete 
information about the vegetation of the whole chain, express the general phyto- 
geographic character of the region. The low eastern Sierra Madre Mountains 
are steep, rough, seamed by numerous canyons and afford a good illustration 
of the arid conditions which prevail east of the Mexican tableland, where the 
limestone of the mountains is contorted and twisted, scarcely half concealed 
beneath a thin covering of soil, which is barely sufficient to support a low, 
dingy, green growth of agaves, cactuses and desert shrubs. 
the western side near Monterey are found Pinus cembroides, associated with Pinus 
latisquama (on the dry calcareous bluffs of gulches), Quereus undulata, ne De ee 
thin forests near the base t). On the higher summits is Pinus teocote, while on the shaded and 
cooler higher slopes, especially in the ravines with northern aspect, are groves or belts Dr er 
dotsuga Douglasii, associated in the ravines toward the base with Cupressus gu ge "The 
Juniperus flaceida and J. tetragona var. oligosperma occur in canyons near the ni u 
sunnier, drier slopes are covered with a dense growth of shrubs consisting of nn RR Q 
Q. undulata and in rich canyons Q. reticulata becomes a tree and grows associated wi R 
Emoryi and Q. virginiana. : 
The foothills u mainly,‘ according to PRINGLE, ledges of limestone with. the are ge 
of cactuses, agaves and a shrubby vegetation consisting of Lindleya mespiloides, a weite 
parvifolius, Cowania plicata, Fraxinus- Greggi, Arbutus xalapensis, Arctostaphylos pungens, 
rhamnus ericoides, Rhus microphylla, Ceanothus Greggii and Epieer up ark the nor- 
he eastern, rain-visited slopes of these mountains south of Monterey = le 
thern limit of Pinus Montezumae. Belts of Carya myrietioasängiEn Po a 
excluding other species, The wet canyons of lower slopes are oceupied by ee RR 
: Juglans rupestris, Quercus polymorpha (attaining a size of two u. by sixty); = REEEETR, 
with maximum diameter three to five feet, Platanus mexicana, Fraxinus viridis, EEE var., 
Tilia mexicana, Chilopsis saligna, Ulmus crassifolia (on river ‚bottoms) ” eds 
Prunus capollin, Planera aquatica, Bumelia lanuginosa var. DER: rn Outside of the 
pulverulenta,. Cornus florida (one foot by twenty five) and Be ne most abundant 
Canyons, several of the above trees mingle with Quercus Grahamil (a small 
a 
1) PRINGLE, C. G.: Notes lign. Veget. Sierra Madre, see Bibliogr. p- 85- 
