THE FOSSIL RECORD 19 



we are fairly safe in believing that cultivated 

 plants came from the related wild forms, and not 

 the other way about. Even this is not always 

 quite certain; in following up the history of the 

 Wheats, the possibility has often had to be con- 

 sidered that an apparently natural form might 

 really be an old cultivated form run wild. We 

 can only be certain of tracing a cultivated plant 

 to its origin if we know its history. This brings 

 us to our main point, the necessity for historical 

 testimony; the analogy of cultivated plants shows 

 us that we can only hope to gain any certain 

 knowledge of the course of descent of plants if 

 we know something of their past history; we need 

 the most direct evidence we can get. 



To a considerable extent such evidence is 

 available. Preserved in the records of the rocks, 

 invaluable though fragmentary chapters from the 

 evolutionary history have come down to us. The 

 importance and interest of the fossil record is 

 recognised by every one as regards the Animal 

 Kingdom. The monstrous Reptiles, the "Dragons 

 of the Air" and the toothed birds, from the Sec- 

 ondary Rocks, the great Sloths and Mammoths 

 of later days, are subjects of popular knowledge; 

 many people are aware of the light that has been 

 thrown on Evolution by the fossil history of the 

 horse and the elephant. 



Fossil plants are less familiar, but, in their 



