EASTERN BORDERS. 297 



We shall now describe the forms of evanished vegetable life, which 

 flourished in this district during the Mountain Limestone era, and 

 whose remains constitute our coal-beds. The species we have been 

 able to determine are not numerous ; but most of them belong to 

 genera characteristic of the Carboniferous formation. We give figures 

 of a few forms which have not previously been described. 



Exogenous Plants. 



Conifers. 



At one period it was believed, that the lowest orders of plants, only, 

 lived during the Carboniferous era. Mr. Witham demonstrated the 

 fallacy of this hasty, negative conclusion ; and it is interesting to 

 notice, that the first distinct evidence was obtained by him from 

 Berwickshire. Fossils were found exhibiting coniferous structure at 

 Lennel Braes, Allanbank, and Tweed ]MiU, where the strata are 

 members of the Mountain Limestone. At Lennel Braes, which is a 

 little more than two miles below Coldstream, on the Tweed, they occur 

 in great abundance in a bed of shale along vdth irregular coaly matter; 

 and also at Allanbank Mill near the junction of the Whiteadder and 

 Blackadder, along with Sigillariee, Lepidodendra, and Fern fronds*. 



Genus Pitus (Witham). 



Only fragments of stems have been found ; they were flattened, 

 tapering, and branched ; the largest fragment was 4 feet long, having 

 a circumference at one end of 6 feet, and at the other of 4 feet ; the 

 bark was converted into coal; the exterior surface was grooved longi- 

 tudinally. Portions retained structure, and showed a medullary axis 

 or pith of large size, surrounded by woody tissue consisting of elon- 

 gated cellules, and having very indistinct indications of concentric 

 circles ; medullary rays proceeded from the pith to the bark; and on 

 the walls of the woody tissue were two or three series of roundish 

 areolae or disks, such as are seen in recent Coniferae. Two species 

 have been determined : they are distinguished from each other by the 

 breadth of the medullary rays. 



Pitus ANTiauA (Witham). Ref. Witham's Fossil Vegetables, t. 3, 



t. 4. f. 1-7, t. 8. f. 1-3. 

 Medullary rays of four or five series of cellules. 

 Localities. Lennel Braes and Tweed Mill. 



Pitus prim.eva (Witham). Ref. Witham's Fossil Vegetables, 

 t. 8. f. 4-6, t. 16. f. 2. 

 Medullary rays of ten to fifteen series of cellules. 

 Locality, Tweed Mill. 



* Witham on Fossil Vegetables. We have recently examined the strata 

 at Lennel Braes and Tweed Mill, and found the Coniferous trees in masses 

 of limestone associated with marine fossils — Spirorbis Carbonarius and 

 undetermined species of Orthoceras Plcurotomaria, and Avicula, ]noving 

 that these plants had been carried into the sea, and there fossilized. 



