458 



THE POPULAR SCIENCE MONTHLY. 



This instability of the environment has produced an instability of the 

 flora, and caused those differences which have resulted in the Europe- 

 an vegetation of our time. 



As before remarked, in speaking of ancient climates, when we go 

 back in time, and particularly Tertiary time, we see the vegetation 

 taking more and more of a tropical character. Hence in these epochs 

 there existed in Europe a multitude of forms which can not live there 

 now. Palms and Cycadeae (Fig. 2) and large, beautiful ferns were 

 long ago exiled. Other forms, as the laurel, the vine, the ivy, have 

 never quitted the region where they were born, or, at least, where they 

 appeared for the first time. 



The number of figures that Saporta has interspersed with his text, 

 representing the principal vegetable types of the past, offer us the still 

 further advantage of comparing species of the same type, and verify- 

 ing by inspection the respective modifications of these species, and 

 their passage from one to the other. Without doubt, we are far from 

 possessing all the terms of all the series ; but what we know of some 

 enables us to judge by analogy that what has happened with one genus 

 may happen with others. See, for example, the forms of Pliocene 

 and Eocene oak (Fig. 7), which show clearly how climate has affected 

 this species from the formation of Gelinden at the base of the Pliocene 

 to the gypsum of Aix, that is, the superior Eocene. The forms repre- 



PiG- 8.— Successive Forms of the LAtmEL TrPE, sho'wing the Passage from Lauras primige- 

 niaioL. Canariemis : 1-3. Laurus primigenia. 4. L.princeps. 5. L. Canariensis. 



sented here belong to the group of oaks with entire leaves ; but there 

 is another group with leaves toothed or lobed, in which we discover 

 analogous modifications. We see that leaves at first oval tend to be- 

 come more and more slender, and these lanceolate forms express very 



