some Notes on the Leaf-trace in the Ferns . 241 
geny); ( 2 ) on the size of the pinnae (a local and individual feature—of 
practically no value in phylogeny). 
The adaxial portion of the pinna-trace is the portion dependent on 
heredity; the abaxial portion is variable in relation to features of the 
individual leaf. 
The form of the adaxial side of the leaf-trace is connected with the 
phylogeny of the Fern in which it occurs; its outline and relations are 
useful as phylogenetic criteria. The form of the abaxial portion is 
dependent upon individual peculiarities, 1 and is therefore of little value in 
phylogenetic criticism. 
The way in which the adaxial part of the leaf-trace gives off part (or 
all) of the pinna-trace is important, as that part of the leaf-trace alters its 
form apparently in response to phylogenetic influences. The actual shape 
of the pinna-trace is of little importance, but the method of development of 
the portion of it which comes from the adaxial side of the leaf-trace appears 
likely to be a useful addition to the criteria of value in the study of the 
phylogeny of the Ferns. 
Summary. 
1. There are two types of pinna-supply from the leaf-trace in the 
Ferns. In the ‘ extra-marginal * type, the portion of the pinna-trace which 
comes from the adaxial side of the leaf-trace is nipped off from the back of 
a ‘ hook *, technically from the abaxial face of the curved leaf-trace ; the 
extreme tip of the adaxial portion of the leaf-trace is continued upward as 
part of the leaf-trace. In the ‘ marginal ’ type, the adaxial portion of the 
leaf-trace (nearest to the pinna) is itself given off to supply the pinna. In 
both types (usually in connexion with large pinnae) a portion of the pinna- 
trace may be derived from the abaxial side of the leaf-trace. 
2. A tabular scheme of the distribution of the two types of pinna- 
supply in the Ferns has been drawn up ; among the Ferns examined, the 
extra-marginal type occurs in 46 genera with 94 species, the marginal type 
is found in 51 genera with 126 species. 
3. With a few exceptions (seven genera), the rule holds that the same 
type of pinna-supply is found in the species of a genus of Ferns recognized 
as such in Christensen’s ‘ Index Filicum \ Even in the exceptions, there is 
considerable agreement between the grouping of the species according to 
1 Among entire-leaved species of the genus Polypodium there have been examined P. vaccini- 
folium, Langsd. et Fisch.; P. lycopodia ides, Linn.; P. percussum, Cav.; P. pustulatum, Foist.; 
P. glaucophyllum, Kze.; P. Xiphias (Moore), Bale. ; P. lingua, Vahl; P. crassifolium, Linn. ; and 
P. punctatum (L.), Sw. In P. vaccinifoliurn, P. lycopodioides, and P. percussum the leaf is short; 
only one or two strands regularly occur in the leaf-trace. In P. pustulatum, P. glaucophyllum, 
P. Xiphias, and P. lingua the leaves are longer ; strands appear on the abaxial side of the leaf-trace, 
in addition to the adaxial pair. In P. crassifolium and P. punctatum, which have leaves longer than 
those of any of the preceding species, there is a strongly developed abaxial system of many strands. 
K 
