LYGINODENDRON 



3 6 7 



passes out, a gap, filled by parenchyma, is left in the 

 wood, which only closes up behind the bundle at a 

 higher level (Fig. 129). When the leaf-trace leaves 

 the wood of the stele, it is at first accompanied by its 

 own secondary tissues, which, as seen in transverse 

 section, form a fan-shaped mass on the outer side of 

 the primary wood (see Fig. 129, l.t. 1 ). As the strand 



Fig. i-$\.—Lyginodendron oldhamium. Part of transverse section, from outer part of 

 stele. jt2, secondary wood ; r, medullary rays ; ci, cambium ; />/j 2 , secondary, >/z, 

 primary, phloem ; s.s., secretory sac ; pd, periderm. X 52. Phil. Trans., W. and S. 

 Will. Coll. 1640. 



passes up through the pericycle, this secondary portion 

 is gradually lost, and has usually disappeared at the 

 level where the bundle divides into two (see Figs. 129 

 and 132). The collateral structure, however, is still 

 maintained. It is only where the leaf-trace finally 

 bends out, to enter the petiole, that this structure 

 changes. Here the phloem begins to encroach on the 

 inner side of the xylem, until, in the leaf-stalk itself, the 



