[ 



- . . 82 CANADIAN FOSSILS. 



The above reasons lead me to anticipate with confi" .,.0 the discovery 

 in the Silurian of a flora similar in type to that of the Lower Devonian, 

 but probably richer in species. 



4. Is it possible to indicate where such earlier flora may be expected 

 to occur ? Whatever views wo may adopt as to the origin of species, it is 

 plain that land animals and plants must originate on the land, and marine 

 animals and plants in the waters. Further, in areas liable to oscillations 

 of level, there must be the more .ibrupt and sudden changes, while in (juiot 

 areas such changes may be slow and gradual. A notable example of this 

 is afforded by the area of the Gulf of St. Lawi'ence. Submerged from 

 the eariiest geological times, and unaffected by the great Appalachian dis- 

 turbances, it presents in the Island of Anticosti an imperceptible transi- 

 tion, elsewhere unexampled in Eastern America, from the Lower to the 

 Upper Silurian. Wherever the earliest and most permanent land existed, 

 there would be the earliest and most continuous flora. As the land ex- 

 tended in area the flora would extend and would be augmented. As in any 

 period the oceanic area encroached on the land, the flora would be driven 

 back on its old centres, and might be diminished in amount and variety. 

 Possibly in periods of extensive submergence, it might over vast areas be 

 destroyed altogether, and on subsequent re-emergence might in the first 

 instance be tardily and imperfectly reproduced, or might appear under 

 entirely new forms. Again, a slowly subsiding area Avould be that most 

 favourable for the preservacion of plants as fossils. An area in process of 

 re-elevation, especially if this were rapid, would be unfavourable, and this 

 more particularly if the previous marine condition had been very extensive. 



In Eastern America, from the Carboniferous period onward, the centre 

 of plant distribution has been the Appalachian chain. From this the plants 

 and sediments extended westward in times of elevation, and to this they 

 receded in times of depression. But this centre was non-existent before 

 the Devonian period, and the centre for this must have been to the North- 

 east whence the great mass of older Appalachian sediment was derived. In 

 I •. • the Carboniferous period there was also an eastward distribution from the 



Appalachians, and links of connection in the Atlantic bed between the Floras 

 of Europe and America. In the Devonian such connection can have been 

 only far to the north-east. It is therefore in Newfoundland, Labrador, and 

 Greenland that we are to look for the oldest American Flora, and in like 

 manner on the border of the old Scandinavian nucleus for that of Europe. 



Again, it must have been the wide extension of the sea of the Cornife- 



' ; reus limestone, that gave the last blow to the remaining flora of the Lower 



Devonian : and the re-clcvation in the middle of that epoch brought in the 



Appalachian ridges as a new centre, and established a connection with 



