Polycycly. 
221 
known form of two slightly curved vascular plates within the inner 
sclerenchymatous ring. Branches from both dorsal and ventral 
strands of this system pass up into the petiole and form the lateral 
folds of the petiolar system. In this case we must suppose that 
decurrent strands from these folds have extended throughout the 
Fig. 66. Ptcris iucisa, transverse sections, (all x G). I.— Ptcris iucisa, 
type (from Gwynne-Vaughan’s preparations). a., stele of internode, b., 
separation of leaf-trace. ( l.t.) c., separation of branch stele ( st .), from base 
of petiolar strand (of Hypolef>is- type). Ptcris iucisa var inUgrifolia. II.— 
Stele of internode. III., IV.—Origin of lateral folds (A, B.) V., VI.— 
Separation of first branch-stele and opening of folds. VII.—IX.—Separation 
of second branch stele, leaving petiolar strand of deeply folded Hypolepis- type. 
Lateral folds and vascular tissue continuous with them, black. From Tansley 
and Lulham. 
internode and become a continuous internal vascular system. It is 
of interest to note that here again a compensation-strand (c.s. Fig 67) 
arises from the internal system and helps to repair the short leaf- 
gap in front of the origin of the trace. Thus in both these species 
