THE STUDY OF FOSSIL PLANTS. 6 



from abroad who may honor the Society with their presence my most cordial 

 regards and good wishes, and to express the hope that the meeting may be in the 

 highest degree pleasant and profitable. 



Though unable to prepare any formal paper or address, I desire to invite your 

 attention for a few minutes to a subject to which I have given some study in recent 

 years, more especially from the point of view of a geologist. 



The study of fossil plants has until lately been comparatively neglected by geolo- 

 gists, in comparison with that of animal fossils. Its interest in connection with 

 the history of life on the earth has been admitted on all sides, and much attention 

 has been given both to the discrimination of species and to the peculiar structures 

 of the more ancient forms of vegetation, but it has by many geologists been quietly 

 set aside as having little bearing on the progress of their science. I propose to 

 make a few remarks on this subject, based principally on my own experience, and 

 preparatory perhai;)S to a more full treatment of the question should I be permitted 

 to attend the winter meeting of the Society. 



The two principal points in which fossil plants can aid the geologist are in the 

 determination of geologic age and in that of climatal conditions. In regard to the 

 former, plants have the advantage of very wide geographic distribution over 

 the continents, and in earlier periods, when climatal distinctions were less marked, 

 more so than at present. In this respect they correspond in some degree on the 

 land to the distribution of the lower forms of marine life in the sea. On the other 

 hand, they are much affected by climate, altitude and station, but scarcely more 

 so than animal fossils. The species and generic forms of plants are, however, of 

 long duration, and are therefore less available for nice discrimination of subdivis- 

 ions of geologic formations than the higher animals. AVith reference to indications 

 of change of climate, and this more especially in the later parts of the geologic 

 series, they are of paramount value anct have afforded the most satisfactory results. 



If we go back to the oldest land flora certainly known, that of the Silurian and 

 Erian or Devonian, though the plants are of strange and peculiar forms and indica- 

 tive of a much greater uniformity of climate than that prevailing at present, they 

 afford valuable marks of geologic time. I have shown that in Canada three sub- 

 divisions are indicated by fossil plants, and this with a great degree of certainty. 

 The oldest is that of the upper beds of the Silurian and the lower Erian, character- 

 ized by the prevalence of FsilopJiyton, Arthrostigma and some rhizocarpean forms 

 like Parka. This holds good over both America and western Europe. The second 

 is that of the middle Erian, of which a prominent type is that of the plant beds of 

 Saint John, New Brunswick. This is remarkably rich in ferns, and with this cor- 

 responds the not infrequent occurrence of drift stems of tree ferns even in the 

 marine limestones and shales of the Corniferous and Hamilton groups in the United 

 States. The rich plant beds of this horizon are apparently very limited in distribu- 

 tion, but wherever they can be found they will yield good geologic evidence. The 

 upper Erian (Chemung and Catskill) shows a poorer flora, but is characterized by 

 the ferns of the genus Arducoptcris, and in some regions by a marvelous abundance 

 of macrospores of Proto-salvinia. These three subdivisions have now been so cor- 

 related with the fossil fishes and the stratigraphy of the system that no doubt can 

 exist as to their validity or their value in determining diflferent horizons. 



Ascending into the Carboniferous we find the same monotonous flora, indicating 

 the prevalence of very uniform conditions over large areas, and probably a low and 

 flat position of the continents and much carbon dioxide in the atmosphere. This 



