STAGES IN PLANT EVOLUTION 43. 



unlike the earth, in her rock -forming they have never 

 repeated themselves. 



CHAPTER V 



STAGES IN PLANT EVOLUITON 



To attempt any discussion of the causes of evolution 

 is far beyond the scope of the present work. At present 

 we must accept life as we find it, endowed with an end- 

 less capacity for change and a continuous impulse to 

 advance. We can but study in some degree the course 

 taken by its changes. 



From the most primitive beginnings of the earliest 

 periods, enormous advance had been made before we 

 have any detailed records of the forms. Yet there 

 remain in the world of to-day numerous places where 

 the types with the simplest structure can still flourish, 

 and successfully compete with higher forms. Many 

 places which, from the point of view of the higher plants, 

 are undesirable, are well suited to the lower. Such 

 places, for example, as the sea, and on land the small 

 nooks and crannies where water drops collect, which 

 are useless for the higher plants, suffice for the minute 

 forms. In some - cases the lower plants may grow in 

 such masses together as to capture a district and keep 

 the higher plants from it. Equisetum (the horsetail) 

 does this by means of an extensive system of under- 

 ground rhizomes which give the plant a very strong 

 hold on a piece of land which favours it, so that the 

 flowering plants may be quite kept from growing there. 



In such places, by a variety of means, plants are 

 now flourishing on the earth which represent practically 

 all the main stages of development of plant life as a 

 whole. It is to the study of the simpler of the living 

 forms that we owe most of our conceptions of the course 

 taken by evolution. Had we to depend on fossil evi- 



