516 CALIFORNIA ACADEMY OF SCIENCES. 



1. Out of 296 species of plants collected by him on the 

 island of Santa Cruz, no less than 48 are entirely peculiar 

 to these islands, and 28 peculiar to Santa Cruz itself. 



2. Of the remaining 248 species nearly all are distinct- 

 ively Oali/ornian — that is, species peculiar to California are 

 very abundant, while common American species, i. e., those 

 common to California and other parts of North America, 

 are very few and rare. The flora as a whole, therefore, may 

 be regarded as distinctively Californian, with the addition 

 of a large number of species wholly peculiar to the islands. 



3. A number of rare species found in isolated patches, 

 and, as it were, struggling for existence, in the southern 

 counties — San Diego and San Bernardino — are found in 

 great abundance and very thriving condition on the islands. 



4. Lavateray a remarkable malvaceous genus of which 

 18 species are known in the Mediterranean region, and one 

 from Australia, but not a single species on the American Conti- 

 nent, is represented on these islands by four species. This is 

 certainly a most remarkable and significant fact. 



Such are the facts. I account for them as follows: 



California, especially the region west of the Sierra 

 Nevada, is geologically very recent. The Sierra region was 

 reclaimed from the sea at the beginning of the Cre- 

 taceous, and the coast region as late as the beginning 

 of the Pliocene. "When first emerged the coast region 

 was of course colonized from adjacent parts. This col- 

 onization was probably mainly from Mexico, either di- 

 rectly or through the Sierra region; for the distinct- 

 ively Californian plants, though peculiar, are more like 

 those of Mexico than any other. Whencesoever it may 

 have been colonized, however, the environment was suffi- 

 ciently peculiar, the isolation sufficiently complete, and the 

 time has been sufficiently long to make a very distinct flora. 



