IX. ASPLEMUM. 157 
in length, and sometimes as much as two feet. They 
appear towards the latter end of May, and reach maturity 
about September, remaining persistent through the winter. 
The stipes is smooth, shining, dark purple, almost black, 
about as long as, or, especially when vigorous, longer than 
the leafy portion of the frond. The fronds have a triangular, 
more or less elongated outline, the lower pair of pininc 
being always larger than the rest, and the apex of the 
frond often much attenuated. The pinnae are pinnate, 
elongate- triangular, standing obliquely and more or less 
alternately on the rachis ; the lower pair are from one to 
three inches long. The ovate or ovate-lanceolate pinnules 
also, especially those on the lower pinna, are pinnate, and 
stand obliquely and alternately. The smaller pinnules, 
and the lobes of the larger ones, are strongly, unequally, 
and more or less acutely toothed. The texture of the 
fronds, when mature, is for the most part rigid, and they 
assume an erect or pendent position, according to the 
conditions of the locality where they grow, which con- 
ditions also affect their size. The mid-vein of the pinnules 
is distinct. In luxuriant fronds the veins become secondary 
midveins, and in the most compound fronds, the lateral 
veins, or venules, sometimes become as tertiary mid-veins, 
the ultimate diA-isions of the frond, and all the principal 
lobes having mid-veins, from which proceed free alternate 
veinlets, either simple or branched, and on these, near the 
junction with the midvein, and on. the inner side, the 
fructification is borne. The sori are distinct, linear, of 
considerable length, covered by a narrow white indusiurn, 
which bursts with an entire margin on the side towards 
its midvein, becomes at length forced asiut.-, and is ulti- 
mately altogether pushed ofl'. Being numerous, the sori 
frequently becomes confluent and cover the entke back 
of the frond. 
The varieties obtusum and acutum differ from the ordi- 
nary condition of the species, on the one hand in the more 
blunt and rounded, and on the other in the more acute 
