168 THE ROCK SPLEENWORTS. 
The rootstock is short, nearly erect and usually roots 
in acrevice well out of ordinary reach. The fronds, some 
six inches or less in length, are broadest at base and taper 
outward to along slender tip that often roots after the 
manner of the walking fern; in fact the whole plant sug- 
gests the latter species and it is not surprising to learn 
that it was once considered a variety of it. It is, however, 
clearly distinguished by its free veins, and mostly single 
indusia, not to mention its pinnatifid fronds. 
The fronds are thick and evergreen. At some dis- 
tance from the tip they begin to be round lobed and these 
lobes grow larger and the cutting deeper as the base is 
approached, until the lowest often. become separate pinne, 
rather rounded triangular in outline. The stipes are 
usually short, but vary in length with the location of each 
plant, being always long enough to lift the blade clear of 
the crevice in which it is rooted. There is consid- 
erable variation in the fronds. Formsthat are pinnate 
nearly to the summit, with ovate pinne, have been found, 
and others with long, sharp-pointed pinne at the base of 
the frond are known. The sori are borne both upon the 
lobes and the tapering apex, many of them opening 
toward the inferior edges. 
The pinnatifid spleenwort is found from New York to 
Illinois, Arkansas and Georgia. Throughout most of its 
range it isextremely rare though in some small sections it 
isnotuncommon. It has been found on limestone, gneiss 
and sandstone and will probably yet be found on shale. 
Within its range the collector is always warranted in 
expecting it, though heis probably destined to be very 
frequently disappointed. 
