18. AMERICAN FERN JOURNAL 
The entire area of Texas, excepting that portion 
lying west of the Pecos River, was more or less thor- 
oughly explored. As many species of ferns are found 
only in that region they are necessarily excluded from 
the list. In the portion of the state east of the Pecos 
thirty-seven species of ferns and ten species and one 
variety of fern allies were found. 
There are two quite distinct fern floras in this region. 
The eastern part of the state receives an abundant 
rainfall; over most of the area east of the ninety-seventh 
meridian the annual precipitation ranges from forty 
to sixty inches. This is a region of low elevations, 
with few outstanding relief features, and for the most 
part it is heavily forested. The geological formations 
are comparatively recent, ranging from the Upper 
Cretaceous through the Tertiary and Quaternary. They 
consist largely of unconsolidated clastics, clays, sands, 
gumbo and alluvium covering most of the surface, 
but occasionally there are local outcrops of sandstone, 
ironstone or marly limestone. Swamps, bogs, bayous 
and sluggish streams prevail. In such a region moisture 
and shade-loving ferns naturally predominate. 
To the westward the rainfall diminishes gradually, 
the annual total amounting to only fifteen or twenty 
inches at the one-hundredth meridian. The north- 
western part of the state is occupied by the Plains, 
and is almost destitute of ferns except for a few species 
in the deep canyons. To the east is the somewhat 
broken, rocky and sparsely forested area of Paleozoic 
rocks, and the black prairies, underlaid by Upper 
Cretaceous deposits. Very few ferns are found in the 
prairie region. To the south is the Coastal Plain, 
extending far up the Rio Grande. To the north of 
this, and occupying a large area in the southwestern 
part of the state, is the rocky, semi-mountainous country 
of the Edwards Plateau, with bold relief features carved 
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