Scott. — On Peduncle of Cycadaceae. 41 r 
looked. There is no doubt, however, as to its homologies, 
but in Bowenia the centripetal xylem of the peduncle is 
evidently in the last stage of reduction. 
Zamia Loddigesii, Miq. 
The peduncle of a female cone of this species was examined, 
and, next to Stangeria , afforded the best example observed 
of centripetal wood. Towards the base of the peduncle most 
of the vascular bundles possess this tissue, and in some it is 
very well developed (see Fig. 10, x 1 ). The centrifugal wood 
and phloem show a very regular radial sedation ; there are 
usually several groups of spiral tracheides to each bundle. 
The elements of the centripetal xylem are, as a rule, found 
at a little distance from the protoxylem, towards the inner 
margin of the small-celled circummedullary zone. The 
elements of the centripetal wood, like those which form 
the bulk of its centrifugal portion, are scalariform tracheides 
(see Fig. 11). They have a rather wavy course, and are often 
quite short, with truncated ends, especially on the side remote 
from the protoxylem. Both these peculiarities are no doubt 
due to late development, taking place at a stage when the 
tissues are too mature to allow of the unrestricted growth in 
length of the newly differentiated tracheides. 
Occasionally a little centripetal xylem occurs in connexion 
with the small leaf-trace bundles passing through the cortex. 
In a male peduncle of the same species no centripetal wood 
could be detected. 
Ceratozamia Mexicana, Brongn. 
In the peduncle of the male cone of this species fairly 
well-marked centripetal xylem sometimes occurs in connexion 
with the principal vascular bundles. It was found best 
developed in the axis of the cone itself, but it also occurs 
throughout the whole length of the peduncle down to its 
base. About half a dozen centripetal tracheides may be 
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