COMPARATIVE ANATOMY OF THE CYCADACER. 455 
they can thus be distinguished clearly as peduncular bundles, 
and not belonging to the stem in which they are found. 
Numerous mucilage-canals, of irregular course, occur in both 
pith and cortex. 
SuMMARY. 
The following are the chief facts resulting from this investi- 
gation :— 
(1) Two young seedlings of Cycas revoluta, Thunb., show very 
well the general morphology of the parts at that stage: the large 
seed, enclosing the connate fleshy cotyledons, each of which is 
conduplicately folded; the insertion of the latter on the stem; 
the plumule with its covering of scale-leaves. The chief points 
in the anatomy of the seedling are: the enormous development 
of the centripetal xylem of the cotyledonary bundles, and the 
occurrence of anomalous rings of secondary thickening in the 
hypocotyl. 
(2) The chief features of the anatomy of the older seedlings of 
the same plant are the following :— 
The extrafascicular strands of secondary thickening imme- 
diately outside the central cylinder, which are collateral in struc- 
ture and for the most part with the normal orientation of parts 
(a single weak strand in one place having, apparently, a reversed 
orientation of parts), these strands developing, doubtless, later 
into the well-known extrafascicular zones of the adult stem. 
The small concentric strands occurring in the cortex of thc 
stem, whieh are entirely of secondary origin, and eorrespond to 
the large cortical concentric strands of the adult plant. 
The large obliquely outgoing strands of the hypocotyl, which 
run through various regions of the cortex, but whose destination 
and homology are doubtful; they possibly represent an effete 
lateral root-system. 
The occurrence of centripetal xylem in some of the leaf-traces 
in the stem, while in some bundles in the leaf-base it has already 
disappeared. 
(3) In the large stem of Cycas media, R. Br., the only feature 
Worthy of special notice is the occurrence of girdle-leaf-traces m 
the cortex having a tendency to assume a concentric structure 
through the extension of their cambium in the form of a circle 
