PRESIDENT'S ADDRESS. Ixxiii. 



with the conditions of those forests. The Carboniferous flora 

 was uniform in character, and gives no indication of zonal 

 differences in temperature ; this is the case with the flora of the 

 Jurassic and the Lower Cretaceous periods. Sir Joseph Hooker, 

 whilst admitting the possibility of drawing legitimate conclusions 

 from their distribution in the past, points out how wide is their 

 geographical range at the present day. The preponderance oi 

 ferns in the Carboniferous period is adduced in proof of the 

 temperate, equable, and humid nature of the coal measure climate. 

 There was possibly a difference of habitat of some of the plants 

 of that period. The vegetation may be divided into upland and 

 lowland types. That of low level surfaces must have been com- 

 posed of dense growths of such plants as could maintain themselves, 

 like the peat vegetation of the present day, for indefinite periods 

 on the same spots. Peat is the present-day example of an 

 accumulation of vegetable matter, corresponding, in all probability, 

 to the conditions under which the debris of Carboniferous forests 

 gave rise to coal. 



" It is not," says Neumayer, " in the towering primaeval forests 

 of India and Brazil, nor the mangrove swamps of tropical coasts, 

 but in the moors of the subarctic zone, that plant-remains are now 

 being stored up in a form that, in the course of geological ages, 

 may become converted into beds of coal." The geographical extent 

 of the Upper Carboniferous flora was exceedingly great ; it is traced 

 from the shores of the Atlantic through the northern half of the 

 world to China, and it is greatly developed in the eastern half of 

 the United States. Similar deposits, with nearly the same vegeta- 

 tion, occur far north in the American archipelago, in Spitzbergen 

 and Nova Zembla. We know nothing of extinct plants, such as 

 calamites, lepidodendra, and siyillarece, and there is no reason for 

 concluding that they could only have lived in tropical forests. 

 Conifers grow now in very severe climates, and only the tree-ferns 

 really indicate warm climatic conditions. At the present day 

 their chief development is in the tropics, where they do not require 

 great heat, only the absence of f tost. Differentiation of temperature 



