406 HISTORICAL GEOLOGY. 



Before and during the early part of the Glacial epoch 

 the islands were a part of the continent. We have already 

 given proof of this on page 393. At that time all was 

 inhabited by the same flora, viz., the indigenous. Before 

 the invasion from the north the islands were separated 

 from the mainland. Then came the northern invasion 

 and consequent struggle between native and invading 

 species the destruction of some natives and the modifi- 

 cation of others and the final result was the California 

 flora as we now know it. But the island flora was spared 

 this conflict, and therefore retained more nearly the orig- 

 inal character of both. In the flora of these islands, 

 therefore, we see a near approach to the flora of both 

 mainland and islands before the separation. 



