508 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
Fig. 7. Cells from the centre of the nodal medullary diaphragm of a Catamites. 
Fig. 8. Longitudinal section of a primary medullary ray with medullary cells at h. 
Fis. 9. Part of a transverse section of a Calamite with the cortex in situ. 
PLATE XXIV. 
Fig. 10. Longitudinal section of the same, x, spores accidentally introduced into the 
fistular cavity. 
Fig. 11. Longitudinal section of a woody wedge, showing the pith, longitudinal canal, 
and secondary medullary rays. 
PLATE XXIII. 
Fier. 12. Barred vessels of Calamites. 
O 
PLATE XXIV. 
Fig. 13. Tangential section of a Calamite near the pith, showing the transverse section 
of the commencement of a branch. 
Fig. 14. Two woody wedges of a Calamites with large vessels. 
Fig. 15. Part of the transverse section of a thin-walled Calamites with a smooth exterior 
to its woody zone. 
PLATE XXY. 
Fig. 16. Inner part of the transverse section of a woody wedge of a Calamites (?) unpro- 
vided with longitudinal canals. 
Fig. 17. Transverse section of a portion of a woody wedge and part of a primary medul- 
lary ray of a Calamites in which vascular laminae encroach upon the primary 
medullary rays. 
Fig. 18. Tangential section of part of a primary medullary ray of the last specimen, 
further enlarged, g , vessels of the vascular laminae ; c, cells of the primary 
medullary ray. 
Fig. 19. Transverse section (natural size) of a thin- walled Calamojpitus, imbedded in its 
dark matrix. 
Fig. 20. Small segment of fig. 19, more highly magnified. 
PLATE XXVI. 
Fig. 21. Small portion from opposite the star in fig. 19, viewed diagonally, and exhibit- 
ing part of the outer surface of the specimen. 
Fig. 22. Tangential section of the same Calamopitus crossing the node in the plane of 
the internodal longitudinal canals, or close to the surface of the medulla. 
Fig. 23. Vertical section of part of the same crossing one of the infranodal canals, l. 
Fig. 24. Similar section across the node in the plane of the two woody wedges above 
and below it. 
Fig. 25. Tangential section of the woody zone of the same near its external surface, and 
viewed as an opaque object. 
