CONTRIBUTIONS TO WESTERN BoTANY No. 17 i 
shrubs where the drainage is slight. But as we go eastward there is an 
imperceptible Eevee of sod grasses till at Alpine there are vast areas 
all covered with sod, forming real prairies, and we come to unmistakable 
prairie vegetation, I see no cause for speaking of the region as being di- 
vided by the 
This is ee of Wooton and Standley’s Flora of New Mexico 
where one is led to expect a marked change on crossing that dribbling 
stream. 
I am told that before the advent of fencing the range the whole region 
from Alpine east was a vast prairie, but now almost everywhere there is a 
forest of live oaks and attendant shrubbery. But one must not think that 
my discussion of the geology embraces the whole region. I mean the groun 
work of the region is an elevated floor of a Cretaceous sea where the rocks 
were mostly limestones. But it is well known that in any vast region like 
thi ed 
at high angles into mountain chains, mostly low ranges, and in others there 
has been an exudation of lavas forming mountains such as the Chisos range. 
rings, but 
except the Pecos and Devil’s river, and the latter is the only one deserving 
the name of river. The mountains rarely reach 6500 feet elevation, and so 
do not seem to have much real forest except here and there in the gulches. 
d they have no alpine vegetation, and so far as I saw no spruce vegetation. 
At cloudcroft there was Middle Temperate vegetation, and the only range 
reaching 9000 feet alt. At Kent and Alpine the hills seemed to belong to 
the Lower Temperate, where the live oaks prevailed. All the rest was 
tropical, shown by the presence of Larrea and Mesquit. On the flanks of 
the low ranges just on the edge of the Tropical are vast areas of Yucca elata 
and macrocarpa, with a few patches of Agave. I have elsewhere given my 
reasons for discarding various species of Yucca and Samuela recognized by 
Trelease. 
Going down to the Rio Grande river from Sonora off the high plateau 
to Del Rio I was greatly Daren gas to find the river wending its way 
along a great plain, and t a gradual infiltration of Mexican plants, 
but there was nothing like ae great change in vegetation Soren Ul at 
Cajon Pass, California, or the region from Kanarrah to St. George, Utah, 
where the life zone limits are conspicuously sharp. It was a gelight to see 
Lepachys columnaris and Gaillardia pinnatifida saying “Hello,” as I passed 
the real prairies of Iowa. The presence of such genera as Engelmannia, 
Lidheimera and Zexmenia spoke unmistakably of the southern nature of 
the vegetation. : 
