COMPARATIVE ANATOMY OF THE CYCADACEX. 117 
The bundles of the central cylinder show no indication of the presence of centripetal 
xylem. 
The bundles composing the cylinder of that part of the cone to which the sporophylls 
are attached are orientated with extreme irregularity. Outside the cylinder are bundles, 
also very variously orientated, some lying sideways, others completely inverted, others 
again having a partially concentric structure; it is to those lying sideways that the 
bundles from the sporophylls unite. 
In the basal region of the sporophyll are several bundles in a row and one or two 
above and below this row. Those in the row eventually resolve themselves into two 
which join on to the bundles of the axis (usually two lying sideways). The lowermost 
bundle appears to fuse with one of these two axial bundles, the small upper bundle 
to unite with the cylinder of the axis independently. 
The material being in such a withered condition, it was rather difficult to follow the 
course of the bundles satisfactorily. 
A female cone of E. Hildebrandtii was also examined, with the result that the 
structure was found to be essentially the same as that of the male cone above described. 
Small, perfectly concentric bundles were observed in the sporophylls. 
CERATOZAMIA LATIFOLIA, Miq., and C. MEXICANA, Brongn. 
Male Cone. 
The cone of Ceratozamia seems, so far as my observations extend, to be unique, in the 
exhibition of an ancient Medullosean character which I can find nowhere else in 
the group of modern Cycads. This peculiarity consists in the possession of an intra- 
fascicular ring of strands, i. e., a zone internal to the central cylinder which, in 
development, is inferior to the latter. Such an internal ring may, in the Medullosex, 
either possess a distinct individuality of its own, as is shown in pl. 7. figs. 1 & 2 and pl. 8. 
fig. 3 of Weber & Sterzel's paper, or the bundles composing it may merely be the outermost 
members of a system of strands permeating the pith in all parts, as in pl. 2. figs. 1 & 2 
of the same paper. In view of this transition existing between the medullary system of 
scattered bundles and the ring of strands immediately internal to the cylinder of the stem ; 
in view, moreover, of the further fact that this internal ring may in certain species 
of Medullosa assume a proportion, as regards the development of its strands, scarcely 
inferior to that of the main cylinder itself, we may, I think, formulate the following 
conclusions— That all the vascular strands internal to the central cylinder of the stem in 
the Medullosee are homologous one with another and belong to the same vascular 
system, and this in spite of the great variation in size and arrangement of these strands 
in the different species; further, that all these medullary strands are homologous with, 
and belong to the selfsame vascular system as, the central cylinder itself, for a continuous 
series of transitional forms exists in the genus between the central cylinder and the 
minutest of the scattered medullary strands. The structure is, probably, analogous to 
that which obtains in the stems of certain Ferns, such as Dicksonia, where in the centre 
SECOND SERIES.—BOTANY, VOL. VI. R 
