140 
Hooker . — On P achy theca. 
EXPLANATION OF FIGURES IN PLATE VIII. 
Illustrating Sir J. D. Hooker’s paper on Pachytheca . 
[The figures on this plate are reproductions of very careful drawings of sections 
of a Pachytheca made by myself under the microscope many years ago. The 
specimen itself has unfortunately been lost ; it differs from that which forms the 
subject of Mr. Barber’s paper in its much thicker walls, smaller cavity, and in the 
more numerous large cells in several series towards the interior, as also in the more 
evident passage of them into the cells of the radial tissue. The drawings were 
compared with the specimen by many observers, and may be confidently regarded as 
accurate representations. — J. D. H.] 
Fig. i. Three specimens of Pachytheca of the natural size. 
Fig. 2. Transverse section of the larger of them. 
Fig. 3. Segment of Pachytheca from the centre to the circumference. 
Fig. 4. Portion of four radiating fibres of the periphery. 
Fig. 5. Portion of the periphery from another specimen, in which the filaments 
are separately imbedded in the mineral matrix. 
Fig. 6. Greatly enlarged view of the cells towards the central cavity of the 
Pachytheca , and filaments from the central cavity, showing their relative dimensions. 
Fig. 7. Similar cells still more enlarged. 
Fig. 8. Filaments from the central cavity. 
Figs. 9-12. Transverse sections of filaments in the central cavity. 
Figs. 2-1 2 all more or less enlarged. 
