UPPER PALEOZOIC FLORAS 321 
environment or for altered conditions. It must be admitted, however, 
that in the interpretation of the environmental criteria afforded by 
fossil plants, relatively little serious study has been given to anything 
other than climate. The ecology of the fossil floras is a new and 
-almost unexplored department of paleobotany, though splendid 
work along certain lines was begun by Grand’Eury. ‘The results 
of differences in soils or in altitude have received little attention. In 
general the conditions of fossilization naturally presuppose the origin 
of the vegetal forms at an elevation not far from that of the water- 
level beneath which they have, in most cases, been preserved, though 
here and there certain types have been regarded as drifted from higher 
altitudes. 
THE DEVONIAN FLORAS 
Probable origin of land flora in Devonian.—From the paleobotanical 
standpoint no period within the existence of land floras is of such 
imminent interest and yet is so little known as the Devonian. ‘This 
fact is no doubt due mainly to the relative rareness of indubitably 
botanical material, its usually fragmentary condition, or its partial 
obliteration through metamorphism. Yet the Devonian period prob- 
ably covers the early development, if not the actual beginning, of 
terrestrial plant life on the earth. It witnessed the origin of ferns, 
scouring rushes, Lycopods, and Gymnosperms, including the earliest 
relatives of the conifers. It is supposed to have given birth to the 
Pteridosperms, a group of seed-bearing ferns (Cycadofices), standing 
in the gap between the ferns and the Cycads. 
Features oj early land plants —The development in early Devonian 
time of flat land surfaces and low coasts whose bays were bordered 
by broad marshes intermittently covered by brackish or fresh waters 
was most favorable for the nearly simultaneous development of a 
terrestrial habit in some of the highly varied types which then popu- 
lated the seas. On some accounts it seems permissible to suppose 
that the ancestors of the land plants were amphibious, perhaps 
growing where exposed only at the recession of the tide. It is, I 
believe, probable that these early plants were but sparsely foliate, 
their leaves being either spinoid or very small, slender, and delicately 
thin. The latter were probably dorsally rolled at first during the 
