FAMILIES OF PLANTS 
19 
wide-creeping. The stout, erect to reclining fronds are borne singly 
on stout stipes, and are often 3 or more feet high. The blades are 
usually 3 times pinnate. 
Lady-fern ( Athyrium filix-femma) .—A medium-sized to large 
fern usually growing in moist shaded situations. Rhizome erect or 
ascending. Fronds 3 to 6 feet long, suberect; stipes short; blades 
lanceolate, 2 to 3 times pinnate, the segments membranous, rounded 
or variously toothed. 
Brittle fern ( Filix fragilis). —A small, delicate fern of shaded, 
rocky or moist situations; very common. The slender, fragile stipes 
are about as long as the blades, which are delicately membranous, 
oblong-lanceolate, commonly 3 to 9 inches long, and nearly or quite 
2 times pinnate. 
Rocky Mountain woodsia ( Woodsia scopulina) .—A densely tufted 
fern of rocky places. Rootstocks densely tufted. Fronds very nu¬ 
merous, 4 to 15 inches long, the stout stipes usually golden brown. 
Blades 1 to 2 times pinnate, the lower surface glandular-puberulent 
and invariably bearing jointed, spreading, whitish hairs. 
PEPPERWORT FAMILY (MARSILEACEAE) 
A small family of plants related to the ferns. They grow in 
shallow water or very wet mud and have creeping stems and small, 
palmately compound leaves with four leaflets. The Waterclover 
(Marsilea oligospora) is probably the only member of the family 
that occurs in the park and it is rarely found. 
HORSETAIL FAMILY (EQTJISETACEAE) 
The horsetails are interesting because they are relics of the coal 
age. During the coal age there were many different kinds of horse¬ 
tails, some of which grew to the size of small trees. Now, however, 
there are only a few kinds left. The stems are hollow and jointed 
and the leaves are reduced to two kinds of structures: toothed sheaths 
at the joints of the stem and little, shield-shaped scales on which 
the spore cases are borne. The stems contain particles of silica. 
Field horsetail ( Eguisetum arvense) .—This plant produces two 
the spore cases are borne. The stems contains particules of silica. 
They are brown in color, 6 or 8 inches in height, and usually un¬ 
branched. These shoots soon disappear and later the green sterile 
shoots develop. These are very much branched, the branches in 
whorls, and may become a foot or more high. 
Scouring-rush ( Eguisetum hiemale ).—The stems of this species are 
usually unbranched and 1 to 3 or more feet high. They are quite 
rough from rows of little tubercles. 
