51 
fronds) and Bnjostacliyum pilosum. Under the same conditions, entire 
fronds arc narrowed below, as in Scolopendnum scMzocarpuni, Among 
tufted fronds, such forms are the rule, as in Diplazium, Bhduium, Pohj- 
podium cticullatum, etc., and, as an example with entire fronds, P, 
C(£spitosum may be cited. . All the lower pinnas are sometimes equally 
and extremely reduced, the largest ones being ^immediately above these; 
such fronds are physiologically like those with long stipes and large, 
lowest pinufe; illustrations are Nephrodium aicullatnm, N. 1685, and 
N. BorderdL 
Fronds with broad bases which are so placed as not to overlap, might 
lose considerable light between the stipes, but in general this space is 
utilized. A long, broad wing on the stipe sometimes extends the assim- 
ilating area, as may be observed in Aspidium decurrens, Leptochllus 
latifolius and Pohjpodium doUchoplmiDi. In many ferns the lowest 
pinnae are flexed forward so that they practically fill the space between 
the frond bases; this is the ease with Nephrodium procurreiis, N. diver- 
silohum, N. cucullatum (lowest functional pinnie), N. 1GS5, N, Bordcnii, 
Humata gaimardiana, Asplcninm caudatum, Pohjpodium Srhneidrri and 
AchrosticJium. Aspleniuni snhnormah has the stipes sufficiently erect 
to bring the large lowest pinnae near together and the raehis is bent 
strongly outward just above these, the upper parts of the fronds being 
divergent and nearly horizontal. Similarly^ the close-set fronds of Chei- 
ropleuria are curved outward and downward above the often cuneate base, 
so that most of the frond slopes downward toward the apices. In many 
cases such as NcpJirodiutn canrscens, N. 1677, Diplazlum doUchosorum, 
D, 1667, and AtJiyrivm silvaticum, the lower pinnae are deflexed into 
the space otherwise lost between the frond bases. Deltoid fronds usually 
reach the same end by a strong basiscopic development of the lowest 
pinnae; this is true in most species of Aspidhim, Hitmata, DavaUia, Chei- 
lanthes, Pfcris and other genera. 
Since half the margin of a frond is longer than its axis, most pinniB, 
being narrowed toward their apices, lose considerable space between their 
distal ends. This form economizes the conduction of water and food 
and is mechanically good because it is compact, but it involves a waste 
of light, which is saved by Nephrodium divcrsUohum and N, liordcnii, 
which broaden toward almost truncate apices. N, 1677 has its pinna? 
somewhat narrow near the base, where they bear large, foliose auricles. 
The pinnae, as well as the fronds of uuibrophilous plants, as is to be 
expected, are in general fitted together so as to utilize all possible light 
consistent with the disposible surface. Nntal)ly perfect mosaics are 
proj^ented by DnvaUia solida, Drvvataedtia WiJImrrm and all fronds with 
trapezoidal or "lunulate" pinme or pinnules, such as are presented by 
Polystichum amahilc, DidymochJaona, Lindsaya xcandens, L, pnlrhella, 
Asplenium resedum, and Adinntnm. The pinnie of Lindsaya pulrhella 
Avould overlap wastefully were they not set at such an angle that they act 
like a grating. ■* 
