410 Scott. — On Peduncle of Cycadaceae . 
more marked in the form which Mr. Seward has named 
Lyginodendron robustum 1 . 
As already mentioned the cells of the pericycle outside the 
bundle often become merismatic, dividing tangentially so as 
to produce a certain amount of new tissue, which usually 
remains parenchymatous, but which, in very rare cases, may 
give rise to a rudimentary vascular strand. 
The chief point, however, which has been brought out by 
the anatomical investigation of the peduncle of Stangeria 
is the presence of centripetal xylem which, in the case of the 
male cone, may attain a development equal to that in such 
foliar organs as the carpels of Cycas , and greatly exceeding 
that in most other Cycadean sporophylls. The general 
bearings of this result will be discussed after some other 
cases have been considered. 
Bowen i a spectabilis, Hook. 
In the peduncles of both male and female cones of Bowenia , 
centripetal xylem occurs, but only to a very small extent. 
There is a great difference in the size of the peduncles, that 
of the female cone being much the thicker, with larger and 
more numerous vascular bundles than those in the male 
peduncle : otherwise the structure is identical. 
There is nothing peculiar in the centrifugal xylem or the 
phloem ; here, as in Stangeria , the phloem is decidedly the 
more developed of the two tissues. Centripetal wood was 
only observed in a few of the bundles, and not more than 
four such elements were found in connexion with any one 
strand. They are separated from the protoxylem by from 
one to three layers of cells. Longitudinal sections show that 
here, also, the elements of the centripetal wood are scalariform 
tracheides. The tissue is present in such small quantity, that, 
but for the analogy of Stangeria , it might easily be over- 
1 Williamson and Scott, loc. cit. Part III, p. 722, Plate XXIII, Fig. 8 : Seward, 
A Contribution to our knowledge of Lyginodendron , Annals of Botany, March, 
1897. 
