8 
Scott. — On the Fertile Shoots of 
As already mentioned, there is in one case (PI. Ill, Fig. 18) some 
evidence for the presence of centripetal xylem in the stele of the main shoot. 
There is, however, no indication of the protoxylem between the centrifugal 
and the apparently centripetal elements ; neither do the other sections con- 
firm the presence of the latter. Most probably such appearances are 
merely due to displacement and compression of portions of the centrifugal 
wood. One would not, in fact, expect centripetal xylem to be represented 
in the main shoot ; in the vegetative stem it is always associated with the 
leaf-traces, and, as the axillary shoot is leafless, there are no leaf-traces 
here. 
In the branch the case is different, for here the stele receives the traces 
of the numerous bracts, so that we may expect to find centripetal xylem. 
But, unfortunately, the preservation is never good enough to show the struc- 
ture clearly. In the best section for the branch-stele (2781) (PI. Ill, 
Fig. 17) one can see that the greater part of the xylem of the bundles is 
centrifugal and in radial series ; a few irregularly arranged elements on the 
inner margin may probably represent the centripetal part of the xylem. 
This applies to the branch-stele after it has expanded and acquired a pith ; 
where it is first given off from the main stele it has a purely centric struc- 
ture, with neither centripetal xylem nor pith (PI. Ill, Fig. 19 and Text- 
fig. 2). 
There is no doubt that the bundles of the bracts themselves are 
mesarch, with a fair amount of centripetal xylem. The case figured with 
the protoxylem nearly central (PI. I, Fig. 3). is from an ‘ appendage ’, but, 
as explained above (p. 7), the structure does not differ from that of an 
ordinary bract. 
The distribution of the sclerenchyma in the axillary shoot is in the 
usual form of a Dictyoxylon hypoderma, sometimes nearly continuous 
(Text-figs. 1 and 2; PI. I, Figs. 1, 5, and 6). The branch has little free 
surface, but on the bracts themselves the fibrous tissue is often well developed, 
occurring on both surfaces but chiefly on the distal side, where it forms 
several often more or less confluent bands (Text-fig. 2 , PI. I ; Figs. 2 and 
6 ; PI. Ill, Fig. 17). The parenchyma of the cortex contains sacs with 
dark contents, similar to those occurring in the vegetative stem (Scott, 
1918, p. 452). 
Discussion . 
The very peculiar characters of the shoots under consideration, and 
in particular their bilateral symmetry and distichous branching, at once 
distinguish them from the vegetative axis and indicate a special function. 
As Grand’Eury said, in speaking of one of his species of Cordaianthus : 
‘ La disposition distique des bourgeons est le signe dune nouvelle destina- 
tion ’ (Grand’Eury, 1877 , p. 329). On general grounds there could be no 
