THE CONQUEST OF THE DRY LAND 191 



and moisture. They were the pioneers for 

 animals, and the simpler plants likewise made 

 higher plants possible. 



According to the rock-record, long ages 

 passed before land plants began. For while 

 there are fossil remains of seaweeds in very 

 ancient rocks, there is no definite evidence of 

 land plants till millions and millions of years 

 had passed. It was not till ages after that 

 (early Tertiary) that grass began to cover the 

 earth like a garment an event with far-reach- 

 ing consequences. 



As to the origin of land plants, there are two 

 theories. It is possible that very simple plants 

 migrated from the sea to the fresh waters, and 

 thence to swampy ground ; and that a fresh 

 start was made there which gradually led to a 

 land vegetation. But one of the most thought- 

 ful botanists of to-day, Prof. A. H. Church, has 

 recently argued that the highly developed shore 

 vegetation of seaweeds may have given origin 

 to the dry-land plants by gradual transformation. 

 There is no doubt that the seaweeds have 

 attained great complexity of structure, and it 

 may be that instead of representing a gorgeous 

 blind alley, they point the way to higher plants. 

 If the coast was slowly raised, as it often was, 



