492 
G wymie- Vaughan .- — Observations on the 
The facts described in this paper have an evident bearing on the 
regions of the C-shaped trace* If the above interpretation of the phenomena 
be accepted it is clear that in the xylem strand of the petiolar trace in the 
neighbourhood of the smaller branchings we have to deal with three distinct 
regions : 
(a) the abaxial curve of the xylem strand ; 
(b) a lateral portion which is going to pass out into the branch ; 
(c) a mass of centripetal xylem that is going to remain in the mother 
trace. 
This makes a line drawn across the adaxial points of departure of the 
branch-traces a very important distinction , 1 because it divides the parent 
trace into portions corresponding to the abaxial (centrifugal) and adaxial 
(centripetal) halves of the presumed ancestral trace. In the larger trace 
these regions are still present, all enlarged but unequally so. The greatest 
extension is experienced by the abaxial curve, but the centripetal xylem 
also increases in volume and may acquire a protoxylem or even two of 
its own. 
DESCRIPTION OF THE FIGURES IN PLATE XIII. 
Illustrating Professor Gwvnne-Vaughan’s paper on The Anatomy of the Leaf in the Osmundaceae. 
(All these figures are from untouched photographs.) 
px. i ., inner protoxylem remaining in the parent trace; px. o., outer protoxylem departing with the 
branch-trace; px., undivided protoxylem ; ad. xy., the adaxial or centripetal metaxylem. 
Photos i and 2. Osmunda Claytoniana. Origin of trace to small secondary pinna. No 
adaxial xylem present, the branch-trace being simply nipped off. (x 140.) Slide No. 1983. 
Photos 3 and 4. Todea superba. Origin of trace to ninth pinna from the base of the leaf, 
(x 140.) Slide No. 2022. 
Photos 5-7. Osmitnda Claytoniana . Three stages in the division of the protoxylem and origin 
of the pinna trace to a fairly large secondary pinna. ( x 140.) Slide No. 1978. 
Photo 8. Todea barbara . Preparation for origin of the trace to the seventh lowest pinna on 
a fertile branch of the leaf. The separating groove of parenchyma reaches to the undivided proto- 
xylem. ( x 140.) Slide No. 1994. 
Photo 9. Todea hymenophylloides. More advanced stage of a similar origin of a pinna trace. 
The xylem of the branch-trace is about to separate. ( x 140.) Slide No. 2025. 
Photos 10, 11. Osmunda regalis , var. palustris, horticultural variety congesta. The origin of 
the traces to the top free pinnae of two branches. In Photo 10 the protoxylem has become definitely 
mesarch and is dividing. In Photo 11 the branch-trace has passed off, but the inner protoxylem 
remains mesarch. (x 140.) Slide No. 1948. 
5 It corresponds, I believe, with a line passing through the 4 marges’ of C„ E. Bertrand. 
