498 STRUCTURE OF SCALES OR BASES OF LEAF STALKS. 
the internal structure of the scales, or bases 
of leaf stalks surrounding the trunks of our fossil 
Cycadites, with that of the corresponding scales 
in the recent species.* 
* In PI. 61, Figs. 2, 3, represent two vertical sections of a 
Cycadites microphyllus from Portland, converted to Chalcedony. 
These slices are parallel to the axis of the trunk, and intersect 
transversely the persistent bases of the Petioles or Leaf-stalks. 
In each rhomboidal Petiole, we see the remains of three systems 
of vegetable structure, of which magnified representations are 
given PI. 62, Fig. 1, 2, 3. We have, first, the principal mass of 
cellular tissue (f) ; secondly, sections of gum vessels (h) irregu- 
larly dispersed through this cellular tissue ; thirdly, bundles 
of vessels, (c), placed in a somewhat rhomboidal form, parallel 
to, and a little within, the integument of each petiole. These 
bundles of vessels are composed of vascular woody fibres proceed- 
ing from the trunk of the plant towards the leaf. See magnified 
section of one bundle at PI. 62, Fig. 3, c'. 
A similar arrangement of nearly all these parts exists in the 
transverse section of the leaf stalks of recent Cycadese. In C 3 'caS 
circinalis, and C. revoluta, and Zamia furfuracea, the bundles 
of vessels are placed as in our fossil, nearly parallel to the inte- 
gument. In Zamia spiralis, and Z. horrida, their disposition 
within the Petiole, is less regular, but the internal structure of 
each bundle is nearly the same. In PI. 62, Fig. A shews the 
place of these bundles of vessels in a transverse section of tl'® 
leaf stalk of Zamia spiralis ; Fig. A. c'. is the magnified appe®''' 
ance of one of the bundles in this section ; Fig. B. c" is the mag' 
nified transverse section of a similar bundle of vessels in tl*® 
petiole of Zamia horrida. In this species the vascular fibre* 
are smaller and more numerous than in Z. spiralis, and the opak® 
lines less distinct. Both in recent and fossil Cycadese the com- 
ponent vascular fibres of these bundles are in rows approximated 
so closely to each other, that their compressed edges give e" 
appearance of opake lines between the rows of vascular fibreS) 
(see PI. 62, Fig. 1, c'. Fig. B, c". and Fig. 3, c'.) These bundle* 
