EXPLANATION OF PLATE 57. 97 



Fig. 5. Longitudinal Sections of Araucaria excelsa, 

 shewing polygonal disks, in double and triple rows, 

 on the surface of the longitudinal tubes. Some of 

 the tubes are without disks, as in all Coniferae. 



Fio;. 6. Transverse Section of Araucaria excelsa. 



a. Portion of concentric annual layer. 



Fio;. 7. Radiating; and concentric structure of a branch 

 of Pinus, as seen by the naked eye in a transverse 

 section; the microscopic reticulations are omitted. 

 (SeeV. I. p. 486. Note.) 



a. a. Concentric annual layers, indicating periodical 

 growth. 



Fig. 8. Longitudinal Section of Pinus, shewing the rela- 

 tive positions of the longitudinal vessels and me- 

 dullary rays. 



a, Longitudinal vessels, forming the woody fibres. 



hj Medullary rays. 



Plate 57. V. L p. 494. 



Sections exhibiting the silicified remains of ConiferaB 

 and Cycadese, in their native bed, between the Portland 

 and Purbeck stone, on the coast of Dorsetshire. 



Fig. 1. Appearance of trunks and roots of large Coni- 

 ferous trees, and of trunks of Cycadites, in the 

 black earth, which formed the soil of an ancient 

 Forest in the Isle of Portland. (De la Beche.) 



Fig. 2. Remarkable concentric Ridges of Stone, around 

 the erect stump of a Fossil Tree in the Isle of 

 Portland. See V. I. p. 495. Note. (Henslow.) 



Fig. 3. Inclined position of the petrified stumps of large 

 Coniferge, and of the bed of black mould and peb- 

 bles in which they grew, near Lulworth Cove, on 

 the Coast of Dorset. (Buckland.) 



GEOL. II. H 



