THE 
HEW PflYTOIiOGIST. 
Vol. VII., No. i. Jan. 31ST, 1908. 
LECTURES ON THE EVOLUTION OF THE 
FILICINEAN VASCULAR SYSTEM. 1 
By A. G. Tansley, M.A. 
University Lecturer in Botany, Cambridge. 
LECTURE IX. 
The Leaf-Trace. Ontogeny. 
[Figs. 96—101]. 
A General View of the Filicinean Leaf-Trace. 
The leaf-trace and petiolar vascular system of Ferns, though 
correlated in a general way with the structure of the stem-stele, 
has a semi-independent course of evolution, which it is necessary 
to consider separately. 
It is mainly to Bertrand and Cornaille 2 , and to Gwynne- 
Vaughan that we owe anything like a comparative treatment of this 
subject during the last ten years, a period which has seen for the 
first time a deliberate treatment, particularly in this country, of the 
problems of Filicinean vascular anatomy from the evolutionary 
point of view. 
The French authors have accumulated a great quantity of 
interesting data, but the method of comparison they employ is based 
on a system of morphological units which seems to have but a 
limited value, at any rate from a phylogenetic standpoint. 
Gwynne-Vaughan has done good service in calling attention to the 
fact that the arched type of leaf-trace or some clearly derived form, 
is found in the vast majority of Ferns and is certainly to be regarded 
1 A Course of Advanced Lectures in Botany given for the 
University of London at University College in the Lent 
Term, 1907. 
2 See especially, Etude sur quelques caracteristiques de la 
structure des Filicinees actuelles, I. Lille, 1902. 
