Polycycly. 2 31 
petiolar system, as the supply of the whole frond does to the stem 
system. 
In the stem of the young plant of Dancea simplicifolia we at 
first have a solenostele, (Fig. 73) afterwards a perforated dictyostele 
(Fig. 74), but the behaviour of the internal strands is fundamentally 
like what we have seen in ArcJiangioptens, except that the internal 
strand sometimes branches into two in its course across the central 
ground tissue (Fig. 74), the branches afterwards again fusing 
into one (E). 
Brebner (’02) points out that the internal strands serve to 
connect directly the root-insertions (at the points of closure of the 
leaf-gaps) with one another, and that from the large curved strands 
formed at these points the leaf traces are given off. Any given root 
probably does not reach the soil till after the related leaf has 
unfolded ; hence the advantage of a direct channel from roots 
already developed below to supply the unfolding leaf. 
The adult structure of the Dancea stem (Fig. 75) appears to 
a 
IV., successive leaf-bases. In A and B leaf-trace II. possess an internal 
strand. a, a' compensation strands from second cylinder filling gap III. in 
the outer one. r., roots. From Rudolph. 
