THE DEVONIAN PERIOD 593 



bearing relatives of the conifers, and probably the "seed-bearing" 

 ferns. 1 The Devonian plants were, on the whole, but sparsely 

 foliate, their leaves being spinoid and small. They perhaps 

 descended from amphibious ancestors, which, in turn, were de- 

 rived from some of the various types of plants which lived in the 

 sea. If so, the expansion of leafage and the development of an 

 aerial system of transpiration were probably evolved slowly as 

 the plants were weaned from their aqueous habitat. The occurrence 

 of most of the fossil remains in fresh or brackish water or lowland 

 deposits gives a suggestion of the habitats of the flora. Of the 

 upland vegetation nothing is known. 



The early Devonian plants appear to have had a strengthened 

 cuticle which helped to support their weight, a function which 

 was discharged later by the woody axes developed by their de- 

 scendants. It is inferred from the fossils that some of the plants 

 were unable to stand alone, but sprawled about on the ground or 

 clambered over other plants. 



The Middle Devonian flora of Maine (Chapman sandstone) is 

 so like a flora of Scotland, Belgium, and the Rhine provinces, as 

 to indicate the probability of the migration of land plants between 

 our continent and Europe, perhaps by way of a land bridge between 

 high latitudes of America and Europe. The Portage flora of New 

 York is found also in Bohemia. In general, the Upper Devonian 

 flora was very similar from Pennsylvania to southern Europe, 

 and this wide-spread flora has something in common with the 

 Devonian flora of Australia. The Devonian fossil woods show no 

 rings indicative of seasonal changes or long periods of drought. 



The types of Devonian plants were similar to those of the next 

 period. The dominant forms were fern-like plants, some of which 

 were seed-bearing, and the lower gymnosperms. The forerunners 

 of the lepidodendrons were present in the Middle Devonian, and 

 before the close of the period the forerunners of the sigillarias 

 appeared. 2 Angiosperms had not yet come into existence, so far 

 as known. 



1 David White, Jour. GeoL, Vol. XVII, 1909. Many of the statements of 

 the following paragraphs are from this article. r 



2 For classification, see p. 944. 



