LAURENTIAN AND EARLY PALEOZOIC. 25 



sver, to realise the idea of arboreal plants haying struct- 

 .res akin to those of thallophytes, but with seeds so 



large and complex that they can scarcely be regarded as 



mere spores. They should perhaps constitute a separate 

 slass or order to which the name Nematodendrece may 



be given, and of which Nematophyton will constitute one 



genus and Aporoxylon of linger another.* 



P Another question arises as to the possible relation of 

 these plants to other trees known by their external forms. 

 The Protostigma of Lesquereux has already been referred 

 to, and Claypole has described a tree from the Clinton 

 group of the United States, with large ovate leaf-bases, to 

 which he has given the name Glyptodendron.\ If the 

 .arkings on these plants are really leaf-bases, they can 

 iarcely have been connected with Nematophyton, because 

 ihat tree shows no such surface-markings, though, as we 

 ave seen, it had bundles of tubes passing diagonally to 

 the surface. These plants were more probably trees with 

 an axis of barred vessels and thick, cellular bark, like the 

 Lepidodendron of later periods, to be noticed in the sequel. 

 Dr. Hicks has also described from the same series of beds 

 which afforded the fragments of Nematophyton certain 

 carbonised dichotomous stems, which he has named Ber- 

 wynia. It is just possible that these plants may have 

 belonged to the Nematodendreae. The thick and dense 

 coaly matter which they show resembles the bark of these 

 trees, the longitudinal striation in some of them may 

 represent the fibrous structure, and the lateral projections 

 which have been compared to leaves or leaf-bases may 

 correspond with the superficial eminences of Nematopliy- 

 ton, and the spirally arranged punctures which it shows 

 on its surface. In this case I should be disposed to re- 



* See report by the author on " Brian Flora of Canada," 1871 and 

 1882, for full description of these fossils. 

 f " American Journal of Science," 1878. 



