212 THE STORY OF THE PLANTS. 



The geological history of the world shows us 

 that the development of plants has been slow and 

 progressive. In the earliest rocks (of which an 

 account is given in another volume of this series), 

 we get few traces of any plants but the lowest : so 

 that at that time it is probable none but seaweeds 

 and their like existed cellular plants which con- 

 tain hardly any parts solid enough for preserva- 

 tion. By the age when the coal was laid down, 

 however, ferns, horsetails, and many gigantic ex- 

 tinct plants with solid stems had begun to exist ; 

 but few or no flowering plants, except conifers, 

 had yet been developed. Later still came the true 

 flowering plants, with covered seeds, at first in 

 simple and antiquated forms, but becoming more 

 complex as birds, mammals, and flying insects of 

 the flower-haunting types were developed side by 

 side with them to visit and fertilise them or to 

 disperse their seeds. Succulent fruits, of course, 

 could only arise when tribes of fruit-eaters had 

 been evolved to assist them ; while such special 

 bee-fertilised types as the sage group, and such 

 complex forms as the orchids and composites, re- 

 quiring the aid of highly-developed insects, are 

 of extremely recent evolution. Plant and animal 

 life have continually reacted upon one another. 



Whoever has been interested in the study of 

 plants by this little book may be glad to know 

 what is the best way of continuing his acquaint- 

 ance with the subject in future. Nothing gives 

 one such a grasp of the facts of botany and of 

 life in general as careful study of the plants which 

 grow in one's own country. Students in the 

 British Isles should therefore buy a copy of 

 Bentham and Hooker's British Flora, and seek by 

 the aid of the key at its beginning to identify for 



