CONIFEROUS TREES OF THE COAL. 



725 



Lign. 166. — Longitudinal section 

 of pine-wood, parallel to a me- 

 dullary ray; showing the row 

 of ducts. 



of this order have since been detected in every formation 

 of later origin. The recent coniferae are arborescent, di- 

 viding into numerous branches, which are disposed in 

 most genera with considerable regularity. The transverse 

 sections exhibit concentric annual lines of growth (as in 

 Lign. 165), and the vertical show the sides of the vessels 

 studded with little ducts {Lign. 166). 



Some of the fossil trees resem- 

 ble the European pines in their 

 internal structure: but the greater 

 number belong to the Araucarian 

 type, which is characterized by 

 the rows of glands being disposed, 

 when double, not side by side, as 

 in Lign. 166, but alternately, as 

 we have previously explained 

 (p. 696).* 



The pine-trees of the coal have 

 but few and slight appearances of the lines by which 

 the annual layers are separated, and resemble in this 

 respect the existing species of tropical regions ; we may 

 therefore infer that the seasons of the countries where 

 the coal-plants flourished were subject to but little diver- 

 sity, and that the changes of temperature were not 

 abrupt. -j- 



In a quarry at Craigleith, near Edinburgh, at a depth of 

 140 feet, part of the trunk of a very large coniferous tree was 

 discovered : its length was thirty-six feet, and the circum- 

 ference of the base nine feet. Polished sections of this 

 stem beautifully display the coniferous structure. A tree 

 fifty-nine feet long, traversing twelve beds of sandstone, 

 has since been exposed ; and as is commonly the case, the 



* In the Koyal Gardens at Kew, there are several nourishing trees 

 of the A . excelsa, and other kinds of Araucariae. 

 f Mr. Witham. 



3 b 2 



