J. LeConte — Flora of Coast Islands of California. 457 



Art. L. — The Flora of the Coast Islands of California in 

 relation to recent changes of Physical Geography ; by Joseph 

 LeConte. 



Some of the results reached by Mr. E. L. Greene in his studies 

 of the flora of the islands off the coast of Southern California* 

 have deeply interested me, because I believe their explanation 

 may be found in geologically recent changes in the physical 

 geography of California. 



These remarkable islands, 8 or 10 in number, are strung along 

 the coast from Point Conception southward, and separated from 

 the mainland by a sound 20-30 miles wide. They are of 

 considerable size (the largest being about 200 square miles in 

 extent), and vary in height from 1,000 to 3,000 feet. They have 

 all the characteristics of continental islands, and are undoubt- 

 edly outliers of the mainland, at one time connected with it, but 

 now separated by subsidence of the continental margin. They 

 may be regarded as the highest points of an old coast range 

 outside of the present coast range, the broad valley between 

 the two being now covered with water. Moreover, the date of 

 the separation may be determined with certainty. That they 

 were connected with the mainland during the later Pliocene 

 and early Quaternary is proved by the fact that remains of the 

 mammoth have been found on Santa Eosa, the largest and one 

 of the farthest off of them.f They were, therefore, undoubtedly 

 separated during the Quaternary Period. 



The main points in Mr. Greene's paper with which we are 

 here concerned are the following " 



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 distinctively Cali- 

 fornian — that is, species peculiar to California are very abund- 

 ant, 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 dis- 

 tinctively 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. 



* Studies in the Botany of California and Parts Adjacent, VI. E. L. Greene. 

 I — Notes on Botany of Santa Cruz Island. Bull. 7, Cal. Acad. Sci. 

 f Proc. Cal. Acad. Sci., vol. v, 15£. 



