292 Count Gaston de Saporta on the Part played 



We might, indeed, suppose that the Flahellarm of the gypsum 

 of Aix, like the Chamcerops excelsa lately planted in our gardens, 

 were capable of bearing several degrees of cold without perish- 

 ing, if these trees occurred isolated in the midst of a multitude 

 of organisms of European physiognomy ; but it would be con- 

 trary to all the data furnished by the study of the laws of nature 

 to extend gratuitously the same supposition to the assemblage 

 formed along with the Palms by the species of Dracana, Mu- 

 sacea, Myrica, Andromeda, Zisyphus, and Rhus, of tropical phy- 

 siognomy, the Laurinece, Bomhacia, Aiiacardiacece, Casalpiniece, 

 and Mimosece, of which the mass encumbers the vegetation of 

 Aix, whilst the species with deciduous leaves, isolated and lost 

 in the midst of the others, would hardly attract attention, if 

 their analogy with their European congeners of the present 

 epoch did not lead us, justly, to attach a very peculiar signifi- 

 cance to their presence. 



In any case, these plants were then only a very limited acces- 

 sory ; it is therefore more simple to inquire how these plants 

 accommodated themselves to a climate which favoured the growth 

 of all tropical forms than to assume that the climatic conditions 

 were established for the smallest portion of the total vegetation. 



Thus, therefore, if we accord to the period of the deposition 

 of the gypsum of Aix and the beds immediately subsequent to 

 it a climate hot enough to cause the presence of the tropical 

 forms, this hypothesis, which is justified by the general facts, is 

 at the same time the negation of a cold season sufficiently severe 

 to produce, by this alone, the stripping of the organisms with 

 deciduous leaves. 



It is nevertheless easy to see that the Tertiary species analo- 

 gous to those which now bear deciduous leaves present no dif- 

 ference from the latter in their consistence, aspect, or any other 

 circumstance; so that we are justified in concluding, from the 

 examination of this category of Tertiary plants, that they lost 

 their leaves periodically in the same manner as the existing 

 plants which reproduce the same model. To cite only the most 

 striking examples. Be tula gypsicola, Populus Heerii, Cratagus 

 nobilis, and Cercis antiqua, in the flora of Aix, and Betula ulna- 

 cea, Alnus prisca, Carpinus cuspidata, and Acer primcEvum in that 

 of Saint-Zacharie, are in this case ; and if there be anything in 

 the texture of their leaves to distinguish these ancient plants, it 

 is a greater delicacy of tissue ; so that it becomes probable that 

 they bore leaves of a finer texture, traversed by nervures of 

 much greater tenuity, than any of the modern species with 

 which they are most nearly allied. 



If the ancient temperature was sufficiently high to exclude 

 the possibility of a cold season, and if, on the other handj the 



