174 EXPERIMENT OF DR. LINDLEY. 



In the lias and oolites, an entirely new race of plants 

 covered the earth. The proportional number of ferns is here 

 diminished : the gigantic lycopodium-like, and cactoid plants 

 of the coal measures, the catamites and palms, all disappear ; 

 but species, undoubtedly belonging to cycadecB, and analogous 

 to plants now natives of the Cape of Good Hope and New 

 Holland, appear to have been common. Coniferous plants 

 were still prevalent, but they were of species which did not 

 exist at an earlier period. 



Tip to this time, the features of vegetation were extra- 

 European, and chiefly tropical, but immediately succeeding 

 the chalk, a change analogous to that observable in the 

 animal kingdom took place. The eocene group is charac- 

 terised by a total absence of cycadece : the number of ferns 

 is strikingly diminished, and conifercB increase in quantity ; 

 while mixed with palms and other tropical monocotyledons, 

 there grew elms, willows, poplars, chesnuts, and sycamores, 

 together with numerous other dicotyledonous plants, which 

 increased in number and variety, till the flora of the more 

 recent tertiary beds has little to distinguish it from that of 

 the present day. 



EXPERIMENT or DR. LINDLEY. The great preponderance 

 of ferns, and the other higher forms of cryptogamic plants, 

 in the flora of the ancient earth, having excited the attention 

 of naturalists, and it being conjectured that the absence of 

 certain genera, and the presence of others, might be accounted 

 for by a difference in the capability of one plant beyond 

 another of resisting the action of water, Dr. Lindley resolved 

 on trying the following experiment. On the 21st of March, 

 1833, he filled a large iron tank with water, and immersed in 

 it 177 specimens of various plants, belonging to the more 

 remarkable natural orders ; taking care to include represen- 

 tatives of those which are either constantly present in the 

 coal-measures, or as universally absent. The vessel was 

 placed in the open air, and left uncovered and untouched, 

 with the exception of filling up the water as it evaporated, 

 till the 22nd April, 1835, when the following results were 

 obtained. 



In the first place, it was found that the dicotyledonous 

 plants, in general, had wholly disappeared, whence it was 

 inferred, that they were unable to remain for two years in 



