374 STRUCTURE OF SCALES OR BASES OF LEAF STALKS. 



A strict correspondence is also exhibited in the internal 

 structure of the scales, or bases of leaf stalks surrounding 

 the trunks of our fossil Cycadites, with that of the correspond- 

 ing scales in the recent species.* 



with circles of cellular tissue, is similar to the two laminated circles near 

 the base of a young stem of Cycas revoluta, (PI. 59, Fig. 3.) This secliaa 

 was communicated to me by Mr. Brown early in 1828, to confirm the 

 analogy which had been suggested from the external surface, between these 

 fossils, and the recent Cycadese ; and is figured in Geol. Trans. N. S, vol. ii. 

 PI. 46, 



* In PI. 61, Figs. 2, 3, represent two vertical sections of a Cycadites mi- 

 crophyllus from Portland, converted to Calcedony, 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 tis- 

 sue (f ;) secondly, sections of gum vessels (h) irregularly 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 

 proceeding from the trunk of the plant towards the leaf. See magnified sec- 

 tion 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 Cycadeis. In Cycas circinalis, and C. 

 revoluta, and Zamia furfuracea, the bundles of vessels are placed as in our 

 fossil, nearly parallel to the integument. 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 shows the place of 

 these bundles of vessels in a transverse section of the leaf stalk of Zamia 

 spiralis; Fig. A. c'. is the magnified appearance of one of the bundles in this 

 section ; Fig. B, c" is the magnified transverse section of a similar bundle 

 of vessels in the petiole of Zamia horrida. In this species the vasculur fibres 

 are smaller and more numerous than in Z. spiralis, and the opake lines less 

 distinct. Both in recent and fossil Cycadese the component vascular fibres 

 of these bundles are in rows approximated so closely to each other, that their 

 compressed edges give an appearance of opake lines between the rows of 

 vascular fibres, (see PI. 62, Fig. i,c'. Fig. B, c" and Fig. 3, c'.) These bun- 

 dles of vessels seem to partake) of the laminated disposition of the woody 

 circular within the trunk. 



An agreement is found also in the longitudinal sections of the Petioles 

 of recent and fossil Cycadca;, PI. 62, Fig. 1, is the longitudinal section 

 of part of the base of a Petiole of Zamia spiralis, magnified to twice the 

 natural size. It is made up of cellular tissue, (f,) interspersed with gum 

 vessels, and with long bundles of vascular fibres, (c) proceeding from the 



