OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
303 
PLATE 49. 
Fig. 8. Transverse section of the central portion of a young twig preparing for 
dichotomous branching. A. One portion of the divided vasculo-medullary 
axis, with an incipient exogenous zone at h. B. The other portion of the 
axis, without an exogenous zone, as in figs. 1 and 2. a. Medullary cells. 
b. Cells of inner bai’k. c. Foliar vascular bundles. Enlarged 18 diameters. 
PLATE 52. 
Lep idode i idron Harcourtii. 
Fig. 9. Transverse section of a young branch \\ inches in diameter. a. Cellular 
medulla, a'. Vasculo-medullary cylinder. a". A segment of a with its 
surrounding inner cortex, b', becoming separated to supply a lateral branch. 
b. Inner bark. c. Foliar vascular bundles, d. Middle bark. e. Parenchy¬ 
matous layer of outer bark. f. Prosenchymatous, or bast-layer of the 
same. g. Leaves. 
PLATE 51. 
Fig. 10. Vasculo-medullary axis with the inner and middle bark of a more developed 
specimen. Enlarged 9 diameters. Pteferences as in fig. 9. 
PLATE 49. 
Fig. 11. Segment of a transverse section of the inner bark of a more matured branch, 
showing a rudimentary exogenous zone. b. Large cells, c". Foliar vascular 
bundles, h. Transversely divided exogenous vascular wedges, li. Deflected 
vessels of obliquely intersected wedges. Enlarged 27 diameters. 
PLATE 51. 
Fig. 12. A branch-bundle, similar to fig. 9, a”, b', but from nearer to the periphery 
of a section, and in a more advanced stage of development, a, a. Vasculo- 
medullary axis. b. Inner bark. c. Foliar vascular bundles, d. Middle bark. 
Enlarged 21 diameters. 
PLATE 53. 
Stigmarian Rootlets. 
Fig. 13. Central portion of a rootlet of the recent Selciginella Martensii. a, a. Xylem 
