Texas PreripopHytTa—lI 19 
from the limestones of the Comanchean series of Lower 
Cretaceous age. Over a limited area in Burnet, Llano 
and Mason Counties igneous rocks, principally — 
and ryolite, occur. 
The ferns of this region are largely yeraph ize, but 
a few species common to the eastward have been able 
to adapt themselves to changed conditions and to 
maintain themselves along the perennial streams in 
the. deep canyons of the Edwards Plateau, where there 
is abundant evidence that the forest flora of the Coastal 
Plain formerly extended. 
The serial numbers of collections refer to specimens 
deposited in the herbarium of the Missouri Botanical 
Garden, while several sets of duplicates were made of 
most of them. During two collecting seasons lists 
were made of ferns noted in addition to specimens 
collected. 
MARSILEACEAE 
MarsILea vesTitA Hook. & Grev. Southerland 
Springs, Wilson County, 10803; Campbelton, Atascosa 
County, 11245; Cotulla, Lasalle County, 11299; Uvalde, 
Uvalde County, 13350; Herrington, Brazos County, 
13444; Byrd, Dimmit County, 13548; Quarry, Washing- 
ton County; Sabinal, Uvalde County; Brownwood, 
Brown County; Alice, Jim Wells County. 
This species appears to be quite common in South- 
western Texas. It is usually found in river bottoms, 
growing in stiff, black, waxy soil, in ditches and slight 
depressions, inundated during part of the year and 
becoming very dry later in the season. As the water 
recedes or dries up the Marsilea fronds spring up, the 
plants fruit and then die down and remain dormant 
until again irrigated. At Byrd, Dimmit County, it 
was found in rather well drained sandy soil. Some 
of the plants are quite robust and densely clothed with 
