BOTANICAL KEMINISCENCES OF SAN FRANCISCO. 169 



by destructive warfare and devastation, in our era it is not so 

 much tlie tearing down, it is the building up that produces 

 these changes, which occasionally are so sudden that a 

 sufficient number of individuals of our own species live long 

 enough to recollect, and eventually note down, what has 

 become extinct and what has been added to the Flora of a 

 region. 



The commemoration of such instances is not only of 

 general interest, it is also instructive, as it frequently gives a 

 clue to the methods of nature in producing such changes. 



Here in San Francisco we have ample field for such 

 observations, but notwithstanding the rapidity of the changes 

 it is high time to fix these observations in print, because the 

 generation which has witnessed them is fast disappearing. 



The landscape which extended in the year 1850 to 1860 

 from Mission Creek to the range of hills at present split by 

 the Second Street cut, was in its greater part filled by swamp 

 and bog and Salicornia flat. A turfy fresh-water formation, 

 inland, gradually merged into the Salicornia flat and was 

 crossed by the serpentine courses of the tide creeks. 



This formation was the basis for a system of sand downs 

 overgrown by shrubbery, or occasionally arborescent 

 vegetation. The downs were mostly arranged in parallel 

 ridges, the ridges being most numerous and frequently 

 confluent towards the mouth of Mission Creek. There were 

 no sand downs on the other side, and its vegetation exhibited 

 an entirely different character, depending on hills of 

 serpentine rock and its debris. 



In the direction of the range, now crossed by the Second 

 Street cut, the sand hills diminished in number and size, the 

 ridges became gradually isolated and stopped entirely at a 

 wide flat, in a locality which is now bordered by Sixth and 

 Third Streets, and entered in a very deep, boggy branch, the 

 sand down region, beyond what is now Mission Street. 



The ridges which enclosed this branch were higher than 

 the rest and reached in considerable elevation the line of 



