Doyvte—Sfio del Fuerte of W. Mexico, and its Tributaries. 67 
All the foothills are covered with a low forest of thorny trees 
and shrubs, leafless in March, but not without blossoms, the “ palo 
blanco” in particular being covered with corymbs of large, white, 
sweet-scented flowers, the food of parrots and deer, and the haunt 
of humming-birds. <A yellow variety of the same species is com- 
mon, and two trees produce large clusters of rhododendron-like 
blossoms, pink and yellow respectively ; logwood of small size is 
abundant, being used for fuel and for stakes. The commonest 
large cactus is the pitahaya a clustering group of dark green 
eylinders about 10 feet high, furnished with grey woolly hair 
near the top, and like all the genus, with chevaux de frise of 
slender sharp spines. ‘There are large echinocacti which are eaten 
greedily by deer, whenever they can penetrate the defensive armour 
of spines and hooks. Thesmaller mamillaria with brilliant starry 
flowers were not generally in bloom in March. Besides the peren- 
nial woody, or fleshy and fibrous plants, there is a numerous and 
beautiful flora of herbaceous varieties that spring up on the advent 
of the rains, and many of them are peculiar to this part of the 
country ; it has been only partially worked out, and there are 
probably many kinds yet undescribed. All the shrubby vegeta- 
tion is much more luxuriant on the recent volcanic area than on 
the eroded spurs of the mesa. 
Proceeding now, from the junction of the Urique river, a new 
series of volcanoes is traversed, the highest being the Cerro de 
San Juan; their form is rounded on top, but with steep slopes, and 
the lava is a dark basic material full of green spherules, which are 
not much elongated in any direction; this lava appears to have 
been exuded in a pasty condition, for it shows no signs of bedding 
or flow. The river has cut a narrow winding gorge through it, 
with steep but not vertical sides. Above San Juan de Dios, at San 
Ignatio, is the junction of the Batopilas river, in a more open 
country ; also showing some signs of alluvial deposits. 
The Batopilas river flows between steep clifis of basalt and 
diorite, apparently lower members of the great plateau series, and 
not recent eruptions like those of San Juan and Realito. Near 
Puebla, granite with numerous dykes and patches of schorl is 
exposed ; and generally the great variety and numerous sections of 
the rocks in this district would make it interesting to a geologist, 
who had time to study them. On account of its ruggedness it is 
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