262 
G wynne- Vaughan. — On the Anatomy of 
present (Fig. 7), until another central strand separated off from the inner 
surface of one of its meristeles. 
The roots arise from the external surface and sides of the stem 
meristeles. A root appears to arise invariably from the point where the 
central strand fuses with a meristele of the ring. The xylem elements 
of the root stele spread out over the outer side of the xylem of the stem 
to form a small attachment-disc of irregular isodiammetric tracheides. 
These tracheides are differentiated very near the apex — at the same time 
as the endarch protoxylems of the stem stele itself, and before the in- 
tervening metaxylem. The roots have a cortex of their own right up 
to the stem stele (Fig. 6, r\ so that there is no ‘ root-pedicel.’ When free 
from the stem the xylem of the root has seven to ten protoxylem groups, 
and its centre is occupied by a few cells of thin-walled parenchyma. There 
is a well-marked endodermis with barred thickenings on its radial walls. 
The Vascular System of the Petiole. 
The arrangement of the vascular strands in the petiole showed a certain 
amount of variation in the three leaves in which it was possible to follow 
their course throughout. On this account it would have been rather difficult 
to fix with any confidence upon those features which may be held as common 
to the leaves of the plant in general, were it not for the light thrown upon 
their interpretation by the structure of the petiole of Kaulfussia aesculifolia . 
Since the number of petioles of Kaulfttssia examined renders the observa- 
tions more reliable, it is advisable to describe the arrangement in this plant 
before going on to that in Archangiopteris . Seven vascular strands are 
given off from the dictyostele of the stem to supply each leaf. They 
anastomose and divide freely as they pass out, so that a varying number 
of separate strands are to be found in the base of the petiole. These are 
arranged in a curve of the form of a widely open arch with its concavity 
facing directly towards the apex of the rhizome (Fig. 8). The two terminal 
strands of the arch (marked x in all the figures) are somewhat larger than the 
rest, and as they pass upwards they approach the median plane of the 
petiole. As they do so they also curve inwards, and at the same time 
turn round so that their protoxylems face away from each other towards 
the sides of the petiole (Fig. 9). This rotation is sometimes continued 
until at a point still further up their protoxylems face almost directly 
towards the median plane (Fig. 10). At a certain point in the enlarged 
basal region of the petiole the terminal strands are usually joined together 
by a transverse suture (^ in Fig. 9) ; sometimes, however, it is the two 
penultimate strands that are thus joined together. 
The several strands so far described are all clearly to be regarded as 
constituting a leaf-trace strictly comparable with the typical leaf-trace of 
