FLORA. 223 



extension of the dicotyledons. The region in which the 

 plants of this class had their first cradle, without being 

 situated in the immediate vicinity of the Pole, could touch 

 it, however, and communicate at the same time with the 

 zones further south. Some day, it is to be hoped, we 

 shall be able to fix the geographical location and probable 

 limits of this mother region of the first dicotyledon ; at 

 present the data are too vague to allow us to think of 

 insisting further on this point. I have been desirous, 

 however, of investigating whether the families of the most 

 ancient dicotyledons, and those the presence of which in 

 the chalk age have been determined in the manner the 

 least doubtful, present in themselves any character which 

 would prove their antiquity. In regard to this the fre- 

 quency and the diffusion of the polycarpic plants, magno- 

 laceae, menispermeae, perhaps berberidaceae, heliboreae, 

 nyrnpheaceae and malvaceae, have not passed unobserved, 

 as the excessive development of certain parts in many of 

 these families have not ceased to reproduce and multiply 

 the types and the subtypes within each of the species. 

 This elaboration has gone on across the last part of the 

 chalk period and throughout the whole of the tertiary, and 

 it continues still in the heart of the polymorphic and 

 floating groups which drive botanists to despair.' 



Thus are we brought to the close of one of the great 

 divisions of geologic eras. 



The rocks in which are found the fossil remains which 

 have been under consideration latterly have been called 

 secondary in contradistinction to the granite, gneiss, and 

 other underlying rocks which have been designated primary 

 rocks. But there are rocks of later formation, which it 

 has been found convenient to distinguish from those again ; 

 and to these the designation ' tertiary ' has been given. 



The fossils found in the older rocks presented little 

 analogy, often no resemblance, to existing plants and 

 animals ; here, however, the similitude is frequently so 

 complete, that the naturalist can scarcely point out a 



