22 BOTANICAL GAZETTE. 



lished in the reports of academies of scit^nce, in the bulletins of geo- 

 logical societies, etc. But the profound lessons derived from these 

 discoveries have hitherto been almost the exclusive possession of sci- 

 entific men. People of general intelligence, who are interested in all 

 progress, have known little of the results obtained. This injustice 

 could be no longer tolerated. A complete treatise was required, writ- 

 ten in a style that all could comprehend, and summine up the progress 

 thus far accomplished : and M. de Saporta. one of the most eminent 

 authorities in vegetable paleontology, has just published such a work." 



"The study of fossil flora not only enables us to follow the evolu- 

 tion of plants from their remotest known ancestors to their present 

 actual descendants, but it throws much light upon the past mysteries 

 of the earth, and especially u))on the climatic conditions which con- 

 trolled its surface while the slow revolutions of organic life were going 

 on." We will quote here and there from the review, not having space 

 for the entire article, although one of great interest to all interested in 

 the history of plants. "There exists between a flora and the climate 

 in which it lives a relation so close that, knowing the one. we can 

 represent the other. Palms do not grow in Greenland nor fir-trees on 

 the plains of equatorial Africa. Each climate has it? flora, and each 

 flora its climate. 



Paleontology has established the permanence and universality of 

 this law ; but it has at the same time established a singular fact which 

 remains inexplicable. It is this : the different climates of the earth 

 have not always been what they are now, either as to temperature or 

 distribution. We speak only of those epochs which have succeeded 

 each other since the time of the most ancient known plants. If we 

 transport ourselves in thought to a time toward the end of the Tertiary 

 period, and then, leaving behind us the Quaternary epoch, follow the 

 course of ages, we find, as an increasing enlargement of the tropical 

 zone, that which is eciuivalent to an increase of temperature for the 

 whole earth. More extended in the Pliocene epoch than in our day, 

 this zone was still greater in die Miocene epoch, and yet greater in the 

 Eocene, and so on till we reach a time when it embraced the whole 

 surface of the earth, bestowing everywhere an equal temperature, 

 feebly oscillating between certain limits. This climatic equality, 

 which, according to Saporta. reaches at least as far back as the time of 

 the coal, would probably cease at the epoch of the lower chalk. Such 

 is the fact established by examination of the flora of different ages." 



"Saporta divides the world of fossil vegetables into four great pe- 

 riods: I. The Primordial or eophxtic, corresponding to the Lauren- 

 tian, Cambrian, and Silurian ; 2. The Carboniferous or paleophytic, 

 comprehending the Devonian, Carboniferous, and Permian; 3. The 

 secondary period or mrsophvtic, commencing with the Trias and reach- 

 ing to the end of the chloritic chalk ; 4. Finally, the Tertiary or fieo- 

 phytic, embracing all the formation from the chalk of Rouen up to and 

 including the Pliocene." 



"The flora of the eophytic period is unknown. The debris \}\{\c\\ 

 represents it has in general a character so vague that there is yet no 

 agreement upon its true nature. The graphite found in the Lauren- 



