INTERPRETATION OF ENVIRONMENTAL CONDITIONS 199 



though it is very probable that some of the types of vegetation were adapted to 

 this habitat. On the other hand, the absence of marine shells from the floor 

 of the coal bed, and the anatomical characters of the fossil plants and condition 

 of life, at the present time, of the descendants and relatives of the coal-forming 

 plant types, show almost conclusively that they were not adapted to live in a 

 habitat of salt-water submergence. Professor Weiss 1 points out that of the 

 living pteridophytes, only a single fern grows where it is subject to marine expo- 

 sure. On the other hand, he calls attention to the fact that the fungi found in 

 fossil Lepidodendron wood and the parasites discovered on the Stigmariae are of 

 fresh-water types, as are also the insect orders to which the eggs found fossil in 

 the bored woods belong. The large size of some of the Calamites, whose trunks 

 sometimes attain a diameter of nearly a foot and a height of 30 feet or more, with 

 the strength and rigidity afforded by thick developments of exogenous wood, 

 should have enabled them, when their bases were embedded in the muds, to offer 

 a relatively strong resistance to such wave-action as may have occasionally 

 been encountered in regions only slightly exposed, but it is not probable that the 

 ancient relatives of our strictly fresh-water horsetail family were able to grow 

 in soil affected by salt water. The large trunks of Sigillaria and Lepidodendron 

 may have offered an effective reinforcement to the calamarian types. Most, 

 possibly all, of the fragments of Carboniferous plants found so rarely in actually 

 marine deposits may well have been brought by drift from terrestrial or fresh- 

 water habitats. 5 On the other hand, it remains most highly probable that the 

 common types of coal of all ages were laid down in fresh or nearly fresh water." 



The beds of the Allegheny series show frequent changes of material due 

 to minor but repeated and rapid fluctuations of level, but, as shown by the 

 quotation from David White just given, they maintain on the whole a 

 homogeneity which speaks of widespread and long-continued uniformity 

 in the general aspect of the land and water. The effect of such an environ- 

 ment upon the vertebrate fauna has been discussed by the author in an 

 account of the amphibian fauna of Linton, Ohio. 3 A small portion of that 

 paper may be repeated here: 



"THE CLIMATIC ENVIRONMENT OF FAUNA. 



"The flora of the region around Linton has been reported upon by David White. 

 His list 4 of the plants of the Freeport group contains no forms differing especially 

 from those of the whole Allegheny series, and all indicate the existence of a 

 'singularly equable and humid but not tropical or even semitropical climate.' 

 There is no evidence either in the woody growth, foliage, florescence, or fruition 

 of any seasonal changes, either of temperature or of humidity. In other words, 

 the animals lived in a period characterized by the extreme monotony of the 



climatic environment. 



"THE ORGANIC ENVIRONMENT. 



"The organic environment of any animal or group of animals may be defined 

 as the group of contacts of that animal with other forms of life. Normally, the 



1 Weiss, F. E., Address to the Botanical Section, British Association for the Advancement 



of Science, Science, vol. 34, 1911, p. 476. 

 1 White, David, Value of Floral Evidence in Marine Strata as Indicative of Nearness of 



Shores, Bull. Geol. Soc. Amer., vol. 22, 1911, p. 221. 

 1 Case, E. C., The Environment of the Amphibian Fauna at Linton, Ohio, Amer. Jour. Sci., 



vol. 44, pp. 124-136, 1917. 

 4 White, David, Bull. Geol. Soc. Amer., vol. I, p. 154, 1900. 



