474 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
PLATE 32. 
Fig. 21. Transverse section of a branch of Halonia from Arran. Enlarged 5 dia¬ 
meters. a. Central vascular axis. b. Innermost portion of the inner cortex, 
c. Outer part of the same, chiefly destroyed, d. Middle cortical paren¬ 
chyma. e. Prosenchymatous cortical layer, f f Large vascular bundles 
supplying the Halonial protuberances. Professor Young and Mr. J. Young, 
Glasgow. 
Fig. 22. Segment of the periphery of the vascular axis of another section of the 
specimen fig. 21. a. Vessels of the central axis. b. Constrictions of the 
axis separating the vessels,/, from it. Enlarged 54 diameters. 
PLATE 33. 
Fig. 23. Similar section to fig. 22, only with the clusters of vessels, f completely 
detached from a to form a bundle supplying one of the Halonial tubercles. 
Enlarged 54 diameters. 
PLATE 32. 
Fig. 24. Similar section to the last, but with the tubercular bundle completely free in 
the inner bark. Enlarged 54 diameters. 
Fig. 25. Similar section to the three last, showing the size of the foliar bundle, b, 
relatively to the tubercular ones. 
PLATE 34. 
Fig. 26. Dichotomous branch of a Lepidodendron terminating in smaller Halonial 
branches. Slightly reduced in size. a. Lower extremity of the branch, 
with oblong leaf-scars like those of L. elegans and selaginoides. b. Leaf- 
scars becoming more rhomboidal. c. Halonial tuberculated portions with 
the rhomboid leaf-scars of Bergeria. Professor Miall. 
PLATE 31. 
Sporocarpon anomalum. 
Fig. 27. Transverse section. Enlarged 55 diameters, a. Canal in the centre of each 
crenulation. 
