FOSSIL PLANTS OF THE CAKBONIFEEOUS SYSTEM. 739 



considers Asterophyllites as having a general affinity with Lycopo- 

 diacese and not with Equisetacese. He finds its parallel in the present 

 flora in Psilotum triquetrum. It is also allied to the fossil plant 

 called Sphenophyllum (fig. 918). Asterophyllites Dawsoni, formerly 

 called Volkmannia Dawsoni, has a peculiar triquetrous vascular axis. 



True Exogenous trees exist in the Coal-fields both of England and 

 Scotland, as at Lennel Braes and Allan Bank, in Berwickshire, High- 

 Heworth, Fellon, Gateshead, and Wide-open, near Newcastle-upon- 

 Tyne, and in quarries to the west of Durham ; also in Oraigleith 

 quarry, near Edinburgh, and in the quarry at Granton. In the latter 

 localities they lie diagonally athwart the strata, at an angle of about 

 30°, with the thicker and heavier part of their trunks below, like 

 snags in the Mississippi. From their direction we infer that they 

 have been drifted by a stream which has flowed from nearly north- 

 east to south-west. At Granton one of the specimens exhibited roots. 

 In other places the specimens are portions of stems, one of them 6 

 feet in diameter by 61 feet in length, and another 4 feet in diameter 

 by 70 feet in length. These Exogenous trees are Gymnosperms, hav- 

 ing woody tissue like that of Coniferse. We see under the microscope 

 punctated woody tissue, the rows of disks being usually two, three, 

 or more, and alternating (figs. 906, 907). They seem to be allied in 

 these respects to Araucaria and Eutassa of the present flora. Dadoxy- 

 lon or Pinites (Araucarioxylon) Withami is one of the species found 

 in Oraigleith quarry ; the concentric layers of the wood are obsolete ; 

 there are 2, 3, or 4 rows of discs on the wood, and 2-4 rows of small 

 cells in the medullary rays. Along with it there have also been found 

 Dadoxylon medullare, with inconspicuous zones, 2, 3, and 4 rows of 

 discs, and 2-5 series of rows of cells in the rays. Pissadendron an- 

 tiquum (Pitus antiqua), having 4-5 series of cells in the medullary 

 rays, and P. primsevum (Pitus primseva), with 10-15 series of cells 

 in the medullary rays, occur at TweedmiU and Lennel Braes in 

 Berwickshire. 



Sir Eobert Christison states- — " Seven fossils, all apparently belong- 

 ing to the Pine tribe, and either to the same species, or to two closely 

 allied to one another, have been uncovered since 1826 in the sandstone 

 of Oraigleith quarry. Six are stems of great trees, and one is a longi- 

 tudinally split section of a large branch, or possibly of another stem. Por- 

 tions of aU seven have been traced as still preserved in Oollections, and 

 have been subjected more or less to examination. Of one, the greatest 

 of aU, about 36 continuous feet, from 12 to 14 feet in girth, have been 

 removed in large fragments to the British Museum, and will be pieced 

 and erected there. Another, found in 1830, is now partly in the 

 Botanic Garden, and has been supplemented by other portions from 

 the Museum of Science and Art, so as to make a nearly perfect fossil 

 stem 30 feet in length. A third, nearly 9 feet in girth, has been sliced 



