OF THE FOSSIL PLANTS EXAMINED. 71 



3. Pence eggensis. 



Cellules A r ery small ; lacunae ; areolae not determined ; medullary rays in 

 their transverse section very short, of 1-8 superimposed cellules. 

 Plate XIV. Figs. 13, 14. Plate XV. Figs. 6, 7, 8, 9. 

 Island of Eig. 



GENUS II. PITUS. 



A medullary axis of very large size ; woody tissue consisting of elon- 

 gated cellules ; concentric circles usually indistinct ; medullary rays ; bark. 



Stems cylindrical or compressed, tapering, branched. Pith of irregular 



polygonal cellules. Woody tissue in the transverse section, presenting the 

 appearance of regular, parallel, radiating series of four-sided, subhexagonal 

 cellules, with interspersed medullary rays. In the longitudinal sections the 

 cellules are seen to be greatly elongated, with oblique or transverse disse- 

 piments placed at great distances. Two of the walls, those facing the me- 

 dullary rays, are regularly reticulated with two or three series of roundish 

 areolae, which are separated from each other. The walls facing the pith 

 and the surface are continuous, and generally destitute of markings. The 

 medullary rays in their transverse sections present irregular series of cellules, 

 varying from four to fifteen. 



The species of this genus have been found in the mountain limestone 

 series of deposits, on the banks of the Tweed. 



1. Pitus antiqua. 



Medullary rays of four or five series of cellules. 



Plate III. Plate IV. Figs. 1, 2, 3, 4, 5, 6. and 7. Plate VII. Figs. 9, 10, 



11, 12. Plate VIII. Figs. 1, 2, 3. Plate XVI. Figs. 9, 10. 

 Lennel Braes, and Tweed Mill, Berwickshire. 



2, Pitus primceva. 



Medullary rays of 10-15 series of cellules. 

 Plate VIII. Figs. 4, 5, 6. Plate XVI. Fig. 2. 

 Tweed Mill, Berwickshire. 



