OF LOWER GREKXSAXD PLANTS. 51 



Blender woody cylinder." From an examination of the type and 

 only specimen the following points can be added. 



The large trunk has evidently been rolled about on the beach, 

 because not only are the usually sharp ridges between the leaf- 

 bases rounded and weatherworn, but it has a number of small 

 beach-gravel pebbles wedged firmly into the deeper angles of 

 the weathered surfaces. The block is cut in half horizontally, 

 and the surface of one half is polished. The texture of the 

 ppecimen is firm and dark, and much more like B. Gibson- 

 ianus, the other Lower Greensand species, than the Wealden 

 B. Sfixbyanus. 



Before cutting, the whole specimen must have been of a 

 flattened oval-lenticular shape, and measured 30x17x22 cm., 

 thus being considerably larger than B. Gilsonianus. The upper 

 end is broken off and weathered, and has been ground down and 

 pounded nearly flat by natural agencies. The general contours 

 suggest that the trunk, when alive, was considerably taller 

 than the 22 cm. now remaining. A number of very deep, 

 almost cylindrical, funnelled-out hollows are present in the 

 weathered exterior, and at first may be taken to represent 

 decayed leaf-bases. These hollows are about 4 crn. deep and 

 1*5-2 cm. across, while between them are thick ridges about 

 1*2 cm. thick. Solms-Laubach remarks on the specimen (1890, 

 transl. 1891, p. 432), and it is evident that he considers them 

 as weathered-out cones. Their lining, which is ribbed by what 

 might might very well have been the bracts, tends to support 

 this view ; on the other hand, they are so numerous that the 

 true leaf-bases appear rather inadequately accounted for if they 

 are all to be reckoned as cones. Owing to abrasion the natural 

 contours are obliterated, and it is impossible to trace the exact- 

 size and shape of the leaf-bases. So far as can be judged from 

 the cut surfaces, parts at least of the internal anatomy are well 

 petrified and should yield good microscopic preparations. 



The pith is 14'5 X 7 em. in diameter. It is impossible to 

 determine its structure, but a few white flecks in the dark 

 matrix suggest the presence of gum-canals. 



The vascular tissue is a hollow cylindrical monostcle. The 

 secondary xylem and phloem form one ring, and originate from 

 a single cambium. The woody cylinder is repeatedly broken by 

 the outgoing leaf-traces. The vascular cylinder is nstoin.shing-ly 



V *> 



