PLANT ARCHAEOLOGY. 277 



remains include the Laurel of the Canaries along with the 

 Vine. The trees of the same epoch farther north were Pines, 

 Lindens, Maples, and Oaks. So, according to Saporta, even 

 the glacial period formed only a seeming interruption to the 

 general course, the steady and really unbroken diminution of 

 terrestrial temperature from the earliest geological periods to 

 the present. This must be admitted if the two classes of ani- 

 mals and plants — those adapted to cold and those to warmer 

 climates — were really contemjjoraneous. Our geologists have 

 maintained that they were not, but that climates have oscil- 

 lated, and that warmer periods than ours intervened between 

 the glacial epoch and the present, or were intercalated in the 

 glacial period itself. But is not the distinction of periods an 

 assumption for explaining the two kinds of fossil remains ? 



We need not enter here into the discussion of the cause of 

 the higher temperature of ancient climates, and of that pecu- 

 liar and temporary state of things attending and originating 

 the glacial epoch, with which Saporta concludes his third 

 chapter. And no space is left us in which to sketch even the 

 outlines of the second pai't and main staple of his book, the 

 history of the vegetable periods, beginning with the " primor- 

 dial marine plants " of the Laurentian and closing with the 

 pliocene, in which existing trees are everywhere identified. 

 The general conclusion of these very rich, elaborate, and well- 

 considered chapters is that the vegetation of the earth has 

 been continuous through all ages, and that the explanation of 

 the present is found in the past. The history of the genus 

 Sequoia — of the two " big trees of California " — as recently 

 sketched by Heer in a popular journal, " Das Ausland," is a 

 fair illustration of this. The difference between these two 

 trees is as notable as their resemblance and their isolation. 

 They are the survivors of a numerous family, of w'ide dis- 

 tribution, which is first recognized in the cretaceous forma- 

 tion, in several species, and which reached its maximum in 

 the middle tertiary, in fourteen recognizable species or forms. 

 Almost from the first these separate into two groups, one fore- 

 shadowing the Coast, the other the Sierra, Redwood, yet with 

 various intermediate forms. These intermediate species are 



