442 MR. W. C. WORSDELL ON THE 
xylem group, while others apparently arise from the region be- 
tween two protoxylem groups. Some of these strands remain close 
outside the central cylinder, with which they once again fuse in 
another part of their course. Others pass farther out, and 
become split up into three or four concentrie strands or parts of 
such. In the outer part of the cortex they assume a vertical 
eourse; their tracheides are twisted about and run in almost 
every direction. These strands, after their parts have become 
fused into a single circular strand, whose centre is occupied by 
short and angular tracheides, die out completely where that part 
of the cortex which they traverse abruptly terminates, and the 
root assumes a much smaller diameter. 
In one place a small strand is seen running off straight to the 
margin of the root. 
All these structures, passing obliquely or radially outward 
from the central cylinder, possibly represent the relies of an 
effete lateral root-system, but of this I can say nothing certain. 
In the other part of the stem occur other very small, round, 
concentric strands which are seen to run up to the base of the 
leaves (fig.6). They probably die out lower down in the stem, but 
this was not traced. Along their vertical course they fuse here 
and there with leaf-traces ; they also branch frequently, and are 
therefore very unequal in size, varying also considerably 1 
shape in different parts of their course; in places they open 0D 
one side, forming a small gap. In the upper part, near their 
termination, the strands become crescent-shaped and collateral 
in structure, and eventually fuse, just under the base of a leaf, 
with a leaf-trace bundle. 
The small strands just described are purely cau 
belonging to a system external to the extrafas 
which occur immediately around the central cylin 
taining to the same category as the cortical ca 
already known to occur in the adult stem of Cycas. 
Some of the leaf-trace bundles, observed in the cortes of the 
stem, have some centripetal «xylem, which is quite couspieu 
many have already lost it while still in the leaf-base. — - 
occurrence of this tissue in these bundles is interesting, 17 it , 
a rarity in the vegetative system, and is here to be considere 
as constituting an abnormal variation from the usual type ° 
structure in these leaf-trace bundles. 
line structures, 
cicular strands 
der, and per- 
uline strands 
