Polycycly. 233 
shorter than the ventral ones. Several strands pass off to the 
petiolar system, leaving a well-marked leaf-gap. There is an 
internal strand (i.s.) which runs freely in the central ground tissue 
towards the lower side, and sends up a branch, which divides into 
two, or two separate branches, below each leaf-gap. These join on 
to the strands bounding the gap and close it in front. Here then 
the behaviour of the internal strand may be compared with that of 
the internal cylinder of Matonia, while Dancea may be compared 
with Saccoloma. 
The basal pulvinus of the Kaulfussia petiole (Fig. 77) shows 
the same phenomenon that we saw in Arcliangiopteris, but the 
internal strands which leave the abaxial strands of the arc and 
cross to the adaxial terminal strands are more numerous than in 
that genus. The internal strands are not continued up as such 
above the pulvinus, but the two terminal strands, with which they 
have joined, fuse together in the median plane, and sink into the 
centre of the petiole as a large strand with adaxially directed proto- 
xylems. This large internal strand is continued up into the rachis 
of the frond and contributes branches to the pinna-traces. 
In Marattia and Angiopteris the stem of the adult plant is not 
elongated, but thick and fleshy, with the surface completely covered 
by the huge leaf-bases. The young plants however show the 
elongated form and their organisation is essentially radial, the 
leaves being given off all round, though in the adult plants there is 
a distinct tendency to dorsiventrality. In the young plants the 
vascular system is organised in fundamentally the same manner as 
in the genera already described, a ring of branching and anasto¬ 
mosing strands surrounding a central one, which behaves as in the 
other cases. 
In the adult stem of Marattia fraxiriea —a comparatively small 
species—there are two concentric rings of strands, i.e., two dic- 
tyostelic cylinders surrounding a central strand. The second 
cylinder here closes the leaf-gap, as the central strand does in the 
simpler forms, and is nearly equivalent to the second solenostelic 
cylinder in Matonia pectinata. There is little doubt that, as in that 
case, it arises ontogenetically by elaboration of the original internal 
strand, though there is no available information on the point. The 
internal strand of the adult stem fills the gap made in the second 
cylinder by sending up two branches to the point of closure, again 
just as in Matonia, and the whole arrangement is materially the 
same. 
