234 Davie.—Comparative List of Fern Pinna-traces , with 
who has given me free access to the rich collections under his charge. To 
him and to Professor F. O. Bower, F.R.S., who kindly supplied me with 
material of several important species, I desire to express my thanks. 
In the present list I have been able to group the forms of pinna-supply 
under two heads. In my last paper 1 I was unable definitely to state that 
there are only the two types. These two types of pinna-supply differ only in 
regard to their derivation from the adaxial portion of the leaf-trace ; if the 
portion (or all) of the pinna-trace derived from the adaxial portion of the 
of pinna-supply in Dryopteris vivipara 
(Raddi), C. Chr. 
Fig. 2. Diagrams to illustrate the 
development of the marginal type of 
pinna-supply in Pteris unibrosa, R. Br. 
leaf-trace comes from the back of a hook, we have the ‘ extra-marginal ’ 
type 2 (Fig. i) ; if it comes directly from the margin (i. e. if the adaxial 
margin of the leaf-trace is given off), we have the ‘ marginal’ type 3 (Fig. 2). 
In either type we may have a portion of the pinna-trace derived from the 
abaxial side of the leaf-trace. This, a local phenomenon, usually appearing 
where the pinnae are large, seemed to be the basis of a potential third type 
1 Trans. Roy. Soc. Edin., vol. lii, pp. 1-36. 
3 Ibid., p. 251. 
2 Ann. of Bot., vol. xxvi, p. 250. 
