238 THE EVOLUTION OF PLANTS 



each of which reached a very high development 

 in its time, and then, as the conditions changed, 

 fell into the background, some new family spring- 

 ing up to take its place. 



The leading Cryptogamic races of the Palaeozoic 

 age, the gigantic Club-Mosses and Horsetails, 

 had lost their importance by Mesozoic times. 

 The great Palaeozoic class of the Seed-Ferns was 

 replaced all over the world by the Cycadophytes, 

 while at the same time true Ferns seem to have 

 become more prominent than before. The Cor- 

 daitese was succeeded by the Coniferse and by the 

 family of the Maidenhair-trees. When Cretaceous 

 times came, the dominant Cycadophytes soon 

 dwindled away and their place was at once taken 

 by the Angiosperms, probably an offshoot of 

 their own stock. This immense change can be 

 expressed in a word, but we have no idea as yet 

 how the revolution was effected, nor how the 

 infinite variety of Flowering Plants was developed. 

 Beyond the probable connection with the Cycads, 

 we know practically nothing as yet of the course 

 of evolution of Angiosperms, though there are 

 good grounds for believing that the Dicotyledo- 

 nous type is more primitive than the Monocoty- 

 ledonous. There is an immense amount of 

 material for the geological history of the Flower- 

 ing Plants, and we cannot doubt that ultimately 

 its investigation will yield important results. 



