OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
359 
Fig. 15. Vertical section of the specimen, fig. 14, passing through a node at n. 
Reference letters as in fim 1 4. Two-thirds natural size. 
O 
Fig. 16. Ttadial vertical section of the vascular cylinder of fig. 14. d. Secondary 
medullary rays. g. Vessels. Enlarged 14 diameters. 
Fig. 1 7. Small portion of another radial section, like fig. 16. d. Secondary medullary 
rays. g. Peculiarly contorted vessels. Enlarged 20 diameters. 
Fig. 18. Transverse section of a small portion of the outer bark, composed of cells 
of prismatic prosenchyma arranged in lines radiating from within 
outwards. Enlarged 26 diameters. 
Fig. 19. Radial section of fig. 18. Enlarged 14 diameters. 
Fig. 20. Tangential section of fig. 18. Enlarged 32 diameters. 
Fig. 21. Portion of a tangential section of the same hark, with a lenticular mass of 
parenchyma passing through it radially. Enlarged 10 diameters. 
Fig. 23. Tangential section of the node of a vascular zone of another Calamite 
intersected near its medullary surface, c, c, c", c" . Primary medullary 
rays separating the primary vascular wedges, f. 1. Clusters of small 
cells located at the upper nodal extremity of each primary medullary ray. 
to, to". Small lenticular areas usually isolated upon the node, as at rn, 
but in one instance, m", connected with the primary medullary ray, c" . 
Enlarged 8 diameters. 
Fig. 24. Similar section to fig. 23, and from the same segment of the same Calamite, 
but made nearer to the cortical surface of the vascular cylinder. The 
cellular masses, l, at the upper extremities of the primary medullary 
rays, fig. 23, c, now appear as isolated lenticular areas, l, enclosed within 
the coalesced vascular wedges f. The primary medullary rays with which 
they are connected in fig. 23 have disappeared, and are only represented 
by dark vertical lines, similar to those shown at c. to. Verticil of lenticular 
cellular (1) areas, apparently identical with those at fig. 23, to. Enlarged 
8 diameters. 
Fig. 25. One of the lenticular areas, l, of fig. 24, further enlarged. 
PLATE 21. 
Fig. 26. Tangential section from the node of a large Calamite cutting, at rn, 
transversely through the medulla of a developing branch. Enlarged nearly 
6 d iameters. 
Fig. 27. Radial longitudinal section of another part of the node of the Calamite, 
fig. 26, passing longitudinally through the medulla of a lateral branch. 
a. Fistular medullary cavity of the primary stem. b. Medullary cells of 
the parent stem. g. Vessels of the same, to, to'. Parenchyma of the 
developing branch, originating in the pith of the parent stem at to', and 
passing outwards. Enlarged nearly 6 diameters. 
MDCOCLXXVITT. 3 A 
