CHAPTER XIX 
SENSITIVE FERN 
Onoclea sensibilis. 
Rootstock wide-creeping, forking, greenish-brown to cherry- 
colored, black in age, hollowed beneath bases of petioles, smooth 
or bearing an occasional large pale-brown scale: leaves scattered, 
borne on all sides of rootstock: roots copious, densely matted, 
springing from edges of hollows, also often continued backward 
or forward in lines from edges. 
Leaves erect, dimorphous: the sterile twelve to fifty-four 
inches bong, leaf-like, sensitive to frost: sporophylls shorter, 
contracted, rigid, paniculate, persisting into second season. 
Petioles usually as long as or longer than blades, sparingly 
furnished with pale brown, concolorous, hyaline, ovate, acute, 
ciliate, often deciduous scales, at base similar in color and paral- 
lel to rootstock, compressed, often elongate or cochleariform: 
above erect, rounded; in sterile leaves slender, slightly furrowed 
on face, green or in spring wine-red, straw-colored in age; in 
sporophylls stouter, slightly flattened or furrowed on face, espe- 
cially near the base, when dried greenish-straw-colored or in age 
pale brown: fibrovascular bundles two, strap-shaped, uniting be- 
low blade into one U-shaped in section. 
Blades of sterile leaves deltoid or ovate-deltoid, below sub- 
