The Evolution of the Filicinean Leaf-trace . 1 
BY 
EDMUND W. SINNOTT. 
With Plate XI and eleven Figures in the Text. 
T HE anatomy of the leaf in the Filicales has recently attracted 
much attention among botanists, for the reason that about it have 
centred some of the most fundamental problems of plant morphology, 
such as those concerning the retention of primitive characters by the leaf, 
the inter-relations of the foliar vascular supply and that of the axis, and the 
general questions of stelar theory and the origin and differentiation of plant 
tissues. Although the structure of the petiole and blade of the mature leaf 
has been worked out in considerable detail in the various fern families by 
several authors, notably Bertrand and Cornaille (1), Thomae (24), &c., and 
although the general relation of its vascular system to that of the stele 
is well known from the investigations of Prof. Jeffrey and others, the more 
minute anatomy of the base of the leaf-trace, as it leaves the central cylin- 
der and while it is still in the cortex or the lower part of the petiole, has 
apparently not received the attention it deserves, for it is in this portion of 
the course of the leaf-bundle that the effects of changing external conditions, 
working upward from the axis and downward from the frond, must be felt 
last and least. It is therefore here, if anywhere, that we should expect 
to find indications of what was the structure of the primitive foliar bundle 
in the ferns. A brief comparative account of the anatomy of this region in 
the main groups of the Filicales, and of the relation of structures here to 
those in the petiole, as well as a discussion of the evolutionary history 
of the order in the light of the results obtained, is the purpose of the present 
paper. 
A considerable number of species were examined by the writer, 2 but 
1 Contributions from the Phanerogamic Laboratories of Harvard University, No. 33 . 
2 These include the following : Osmunda cinnamomea , L., 0. Claytoniana , L., and 0. regalis , L. ; 
Todea barbara , T. superb a, and T. hymenophylloides ; Helininthostachys zeylanica , Botrychium 
virginianum , (L.) Sw., and Ophioglossum vulgatum, L. ; Marattia alata and Danaea alata ; Lygodium 
dichotomum , Aneimia fraxinifolia , and Schizaea pusilla , Pursh ; Gleichenia Speluncae, G. circinata 
v. macrophylla , G. dicarpax. longipinnata , G. rupestris , and G. dichotoma ; Cyathea Macarthuri 
(young plant) ; Dennstaedtia ( Dicksonia ) punctiloba , Moore ; Onoclea sensibilis , L. ; Pteris 
T Annals of Botany, Vol, XXV. No. XCVII. January, 1911.] 
