454 MR. W. C. WORSDELL ON THE 
The course of the separate strands composing the cylinder is, 
as in all Cycads, extremely irregular and sinuous. 
The cortex exhibits, in transverse section, great numbers of 
wedge-shaped leaf-trace bundles of various sizes and of irregular 
course, isolated or fusing together. In longitudinal section of a 
leaf-traco bundle, the tracheides are seen to have all of them 
scalariform pittings on their radial walls. 
The wide pith contains a great number of bundles. These 
are seen to occur in groups or series at regular intervals 
upwards through the stem. Each group represents a cylinder of 
bundles emanating from a peduncle situated in a lateral position 
on the stem. Solms-Laubach* first explained in detail the whole 
structure, showing that the stem of a Cycad was constructed on 
the sympodial system (thereby confirming Karsten’s and 
Warming's observations); the peduncle, which originally con- 
stituted the terminal portion of the stem and contained the apical 
meristem, finally, with the ripening of the cone, ceases its growth 
in length. The growth in length of the stem is continued by 4 
lateral branch, which, arising near the base of the peduncle, by 
its increase in diameter and the expansion of its tissues gradually 
presses the latter organ to one side, enclosing its basal portion 
within its own tissues. In this way in an old stem a succession 
of peduncular cylinders comes to be embedded within the stem. 
The course of these was very well observed in Ceratozamia. The 
lowest of them was seen to enter the pith from the cortex m à 
perfectly horizontal, those higher up in a more oblique and 
gradually ascending, direction. As soon as the cylinder enters 
the pith its bundles begin to branch and spread out in all direc- 
tions, eventually fusing on all sides with the cylinder of the stem. 
These bundles vary considerably in size and in structure. In 
some a cambium has formed, opposite the protoxylem, xylem and 
phloem with inverted orientation of parts; but the tracheides 0 
the xylem are few in number, irregular in shape, and but slightly 
lignified, while the phloem is extremely rudimentary. The moi 
lary bundles differ in shape and appearance from the leaf-traces 0 
the cortex in the fact that the tracheidal rows of the xylem do 
not converge to a point so as to give the wedge-like character 
the bundle, but are spreading and curved on their inner side ; 
* “Die Sprossfolge der Stangeria und der übrigen Cycadeen,” Bot. Zeit- 
1890. 
