158 ON THE FORMATION OF COAL v 



ferns are hard to distinguish from existing ones. 

 At the same time, it must be remembered, that 

 there is nowhere in the world, at present, any 

 forest which bears more than a rough analogy with 

 a coal-forest. The types may remain, but the 

 details of their form, their relative proportions, 

 their associates, are all altered. And the tree-fern 

 forest of Tasmania, or New Zealand, gives one only 

 a faint and remote image of the vegetation of 

 the ancient world. 



Once more, an invariably-recurring lesson of 

 geological history, at whatever point its study is 

 taken up : the lesson of the almost infinite slow 

 ness of the modification of living forms. The 

 lines of the pedigrees of living things break off 

 almost before they begin to converge. 



Finally, yet another curious consideration. Let 

 us suppose that one of the stupid, salamander-like 

 Labyrinthodonts, which pottered, with much belly 

 and little leg, like Falstaff in his old age, among 

 the coal-forests, could have had thinking power 

 enough in his small brain to reflect upon the 

 showers of spores which kept on falling through 

 years and centuries, while perhaps not one in ten 

 million fulfilled its apparent purpose, and repro 

 duced the organism which gave it birth : surely 

 he might have been excused for moralizing upon 

 the thoughtless and wanton extravagance whicli 

 Nature displayed in her operations. 



But we have the advantage over our shovel- 



