THE ORIGIN OF PLANT LIFE ON THE LAND. 



99 



exogens. This unique specimen, found by Hall in the 

 Devoniin of the shores of Lake Erie, is a fragment of 

 mineralised wood, the structures of which are represented in 

 Fig. 94. The large ducts seen in cross section in Nos. i, 2, 



Fig. ^T.—Calamiies radiaius (Brongniart). Middle Devonian of N. Brunswick. 



and 3, and in longitudinal section in Nos. 4 and 5, and the 

 medullary rays, seen in Nos. i, 4, and 6, testify to the fact that 

 this chip of wood must have belonged to a tree of the same 

 type which contains our oaks, maples, and poplars; a type 



a 2 



