25. Under the empire of heat and humidity and in consequence of the excess of carbonic acid dispersed into the air – a gas improper for the respiration of terrestrial animals but necessary to the plants – the exposed terrains were quickly covered with a pungent vegetation while at the same time aquatic plants multiplied on the surface of marshes. Plants, which in our day are simple herbs a few inches high, attained a prodigious height and magnitude; there were then forests of tree-like ferns from eight to ten yards in height, and of proportionate magnitude; plants called wolfs foot, and a kind of moss of the same size, equisetum arvense, * four or five yards high, which we hardly see now. At the end of this period pines or fir-trees began to appear.
* A marsh-plant commonly called horsetail.