302 On the Deciduous Plants of the Tertiary Floras. 



the ancient organs, when compared with those which corre- 

 spond with them in the present day, almost always appear con- 

 siderably smaller, and sometimes even very much so. The 

 silicified trunks of Palm-trees indicate the existence of small 

 species, of which the stem, even in the largest forms, scarcely 

 equals that of Chammrops excelsa in diameter. The Pines 

 only present slender and sparingly divided branches. The 

 leaves of Dicotyledonous plants are almost always small, narrow, 

 oval, elliptical, or linear ; and although very large trees may 

 have small leaves, the persistence and generality of this character 

 cannot but raise great doubts as to the size of the individuals to 

 which they belonged. This doubt has the more foundation as 

 most of the Proteacea most nearly allied to species of Aix in the 

 present order of things only form shrubs of middle size or even 

 mere bushes. 



These data may be applied to the series of species with deci- 

 duous leaves in the flora of Aix ; but for them there are further 

 reasons which would lead to the belief that they were still smaller 

 in their dimensions than the preceding. These plants, not nu- 

 merous as species, and very rare as individuals, are subordinated 

 to organisms in which the variety of combinations and the pro- 

 fusion of forms indicated a development arrived at its climax ; 

 it is among these that we must of course find the strongest spe- 

 cies of the epoch. It appears to us more probable, in fact, that 

 we should find the arborescent organisms of that period amongst 

 the groups as to the preponderance of which there is no ques- 

 tion, such as the Palms, Proteacece, Laurinece, Anacardiacece, and 

 Leguminosce, than amongst the scarce plants with deciduous 

 leaves, which had so inconsiderable a part to play. Considered 

 in themselves, these species, by the knowledge we possess of 

 their organs, confirm the supposition that they only attained to 

 small dimensions. If we except Alnus antiquorwn, the leaves 

 of which were probably persistent, like those of A. nitida and A. 

 Nepalensis, and Cercis antiqua, which only difiers from its living 

 congener in the outline of its leaves, the appendicular organs of 

 the other species with a European physiognomy, either by their 

 comparative smallness or by the analogy of the forms which 

 correspond with them at present, indicate rather shrubs than 

 true trees. There can be no doubt in this respect with regard 

 to the Ribes, Cratagus, and Paliurus, which are only bushes. 

 But, among others, Betula gypsicola belongs to a section of the 

 genus which contains species of very small size, and which is 

 characterized by Hegel, the author of the Monograph of the 

 Betulacese, as " Frutices plerumque humiles ;" Popuhis Heerii is 

 remarkable for the smallness of its narrow saliciform leaf, be- 

 yond any existing Populus of the section Balsamea, to which it 



