THE CARBONIFEROUS AGE. 131 



resembled them in this. But others, to which the 

 name Calamodendron, or Keed-tree, has been given, 

 had stems with thick woody walls of a remarkable 

 structure, which, while similar in plan to that of the 

 Mares' Tails, was much more perfect in its develop- 

 ment. Professor Williamson has shown that there 

 were forms intervening between these extremes ; and 

 thus in the calamites and calamodendrons we have 

 another example of the exaltation in ancient times 

 of a type now of humble structure ; or, in other words, 

 of a comprehensive type, low in the modern world, but 

 in older periods taking to itself by anticipation the 

 properties afterward confined to higher forms. The 

 gigantic club-mosses of the Coal period constitute a 

 similar example, and it is very curious that both of 

 these types have been degraded in the modern world, 

 though retaining precisely their general aspect, while 

 the tree-ferns contemporary with them in the Palaeo- 

 zoic still survive in all their original grandeur. 



Barely in the swampy flats, perhaps more frequently 

 in the uplands, grew great pines of several kinds ; 

 trees capable of doing as good service for planks and 

 beams as many of their modern successors, but which 

 lived before their time, and do not appear even to 

 have aided much in the formation of coal. These 

 pines of the Coal-period seem to have closely resem- 

 bled some species still living in the southern hemi- 

 sphere ; and, like the ferns, they present to us a vege- 

 table type which has endured through vast periods 

 of time almost unchanged. Indeed, in the Middle 



