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s 



tation. Some casts of plant stems found near Cincinnati havebeen 

 described by Mr. Lesquereux as the remains of land plants, but in my 

 judgment other proof of the existence of land vegetation in the Lower 

 Silurian age must be furnished before we can make any positive asser- 

 tion on the subject. 



In the Upper Silurian age, narrower/but still extensive_ portions 

 of our old continent suffered submergence, and in the deposits of this 

 second sea we have indisputable evidence of the existence of land 

 plants. These have been found in Michigan and Canada, and con- 

 sist of the remains of ferns, lycopods, equiseta and conifers, but the 

 specimens are small in size and comparatively few in number, and 

 hence we may infer that land vegetation was not abundant. We are 

 also warranted in the inference, since we have in this earliest 

 known land flora the highest group of cryptogams — the acrogens, and 

 the still higher gymnosperms— that this is not the real beginning of the 

 land flora, and that something simpler and older existed and will 

 probably be discovered. As before, there were seaweeds in great 

 abundance in the Upper Silurian sea. 



The subsidence which gave us the series of sediments we now call 

 the Devonian system, was less extensive than those which took place 

 before the area of permanent land was greater; and the proofs that 

 this land was covered with a luxuriant, beautiful and varied terrestrial 

 flora are conclusive. We have of course made but a beginning m the 

 disinterment of the remains of this flora, but we have already learned 

 enough of it to sketch in clear and strong lines its principal botanical 



features. 



Dr. Dawson has described from the Devonian rocks of Canada 

 and New York, more than a hundred species of Devonian fossil 

 plants. These include conifers of several genera, ferns in considera- 

 ble number, and not a few lycopods and equiseta. Within the United 

 States the most interesting Devonian plants have been found in the 

 Corniferous limestone of Ohio, and the Hamilton rocks of Gilboa, N. 

 Y. In this age, a chain of islands ran down from Lake Erie to Ten- 

 nessee, and, in the limestone which accumulated in the sea surround- 

 ing these islands, quite a large number of plant remains havebeen 

 found. These seem to have been floated off from the Cincinnati 

 island and water logged in the adjacent ocean. The trunks of tree- 

 ferns representing three genera, with a number of smaller plants, have 

 been already obtained from the insignificant excavations of the quar- 

 ries at Delaware and Sandusky. At Gilboa we have the old shore 

 upon which the plants grew, and here again we find tree ferns of 

 several kinds, some of the trunks attaining a diameter of two feej. 



and that singular Psilo^hyton of Dawson apparently connecting the 



lycopods and ferns, and widely diffused in the Devonian age 



The Carboniferous flora was but a continuation ana exijai.s.u.. ui 

 the Devonian. It has been so fully revealed in our excavation of the 

 coal beds, and has been so well studied, that all its general features 

 have come to be familiar to every student of geology. No lengthy 

 description of the coal flora, rich and interesting as it is, is therefore 



