TRAN S ACTION S. 
I. — On the Leaf-Trace in some Pinnate Leaves. By R. C. Davie, M.A., D.Sc., 
Lecturer in Botany in the University of Edinburgh. Communicated by 
Dr R. Kidston, F.R.S. (With One Plate.) 
(Read February 7, 1916. MS. received February 25, 1916. Issued separately February 16, 1917.) 
In a general survey of the pinna-traces of Ferns (Davie, ’14), the results of which 
have been summarised in tabular form ( loc . cit., p. 354 ), two main types of pinna- 
trace were described and contrasted. In the one^the “ extramarginal ” — the pinna- 
trace leaves the back of the hook formed by the incurved edge of the leaf-trace ; in 
the other — the “ marginal ” — the outwardly directed margin of the leaf-trace is 
simply nipped off as the pinna-trace. The more primitive Ferns in the evolutionary 
scale, and the first leaves of both primitive and advanced Ferns, exhibit the marginal 
type of pinna-trace ; the extramarginal type of pinna-trace is found in those Ferns 
which stand midway between the extreme types in the system of classification, and 
in some advanced forms. There is little doubt that the type of pinna-trace is in some 
degree dependent on the systematic position of the Fern which possesses it (ibid., 
pp. 354 , 362 ). On the other hand, there is apparently a relationship between the 
type of pinna-trace and the size and degree of division of the lamina of the leaf in 
which it occurs (ibid., pp. 369 , 372 , 376 ). Further, the same type of pinna-trace seems 
regularly to occur in the species of any genus of Ferns (ibid., p. 354 ). That there 
area few exceptions to each of these generalisations (ibid., cf. pp. 354 , 372 , and 373 ) 
made it desirable that a concise problem dealing with them all should be attacked in 
material grown under natural conditions. A visit to Brazil, in which I was aided by 
a Treasury grant, gave me the opportunity to collect species of the genera Dryopteris, 
Aspidium, Polystichum (which stand midway in the systematic grouping of the Ferns), 
Polypodium, and Leptochilus (which are “ advanced” genera). Species of the genus 
Polypodium were found in such different natural conditions as the bed of a stream, 
the top of a wall, the exposed surface of a sandy strip of land near the sea, and 
the moist shaded depths of a dripping rain-forest. Short-leaved and long-leaved 
Polypodiums were found in these situations, and in more than one instance 
examples of the same species were found under different natural conditions. A 
TRANS. ROY. SOC. EDIN., VOL. LII, PART I (NO. 1). 1 
