51 
fronds) and Dryostachyum pilosum. Under the same conditions, entire 
fronds are narrowed below, as in Scolopendrium schizocarpum. Among 
tufted fronds, such forms are the rule, as in Diplazium, Blechnum, Poly- 
podium cucullatum, etc., and, as an example with entire fronds, P. 
ccespitosum may be cited. All the lower pinnae 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 pinnae; illustrations are Nephrodium cucullatum , N. 1685 , and 
N. Bordenii. 
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 , Leptochilus 
latifolius and Polypodium dolichopterum. In many ferns the lowest 
pinnae are flexed forward so that they practically fill the space between 
the frond bases; this is the case with Nephrodium procurrens , N. diver- 
silobum, N. cucullatum (lowest functional pinnae), N. 1685, N. Bordenii, 
Ilumata gaimardiana, Asplenium caudatum. Polypodium Schneideri and 
Achrostichum. Asplenium subnormale has the stipes sufficiently erect 
to bring the large lowest pinnae near together and the rachis is bent 
strongly outward just above these, the upper parts of the fronds being 
divergent and nearly horizontal. Similarly, the close-set fronds of Ghei- 
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 Nephrodium canescens, N. 1677 , Diplazium dolichosorum, 
D. 1 667, and Athyrium 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 Aspidium, Ilumata, Davallia, Ghei- 
lantlies, Pteris and other genera. 
Since half the margin of a frond is longer than its axis, most pinnae, 
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 diversilobum and N. Bordenii, 
which broaden toward almost truncate apices. N. 1677 has its pinnae 
somewhat narrow near the base, where they bear large, foliose auricles. 
The pinnae, as well as the fronds of ombrophilous plants, as is to be 
expected, are in general fitted together so as to utilize all possible light 
consistent with the disposible surface. Notably perfect mosaics are 
presented by Davallia solida, Dennstaedtia Williamsi and all fronds with 
trapezoidal or “lunulate” pinnae or pinnules, such as are presented by 
Polystichum amabile, Didymochlaena , Lindsaya scandens, L. pulchella, 
Asplenium resectum, and Adiantum. The pinnae of Lindsaya pulchella 
would overlap wastefullv were they not set at such an angle that they act 
like a grating. 
