172 ANCIENT PLANTS 



small-leaved Calamites and Lepidodendrons which ovei- 

 topped them. 



Indeed there is no indication from geological evi- 

 dence that so late as Palaeozoic times there was any 

 great abnormality of atmosphere, and from the internal 

 evidence of the plants then growing there is everything 

 to indicate a dry or physiologically dry 1 sunny condition. 



Of the plant fossils from the Coal Measures we have 

 at least two types. One, those commonly found in 

 nodules in the coal itself; and the other, nodules in the 

 rocks above the coal which had drifted from high lands 

 into the sea. 



The former are the plants which actually formed the 

 coal itself, and from their internal organization we see 

 that these plants were growing with partly submerged 

 roots in brackish swamps. Their roots are those of 

 water plants (see p. 150, young root of Calamite), but 

 their leaves are those of the ''protected" type with 

 narrow surface and various devices for preventing a loss 

 of water by rapid transpiration. If the water they grew 

 in had been fresh they would not have had such leaves, 

 for there would have been no need for them to economize 

 their water, but, as we see in bogs and brackish or salt 

 water to-day (which is physiologically usable in only 

 small quantities by the plant), plants even partly sub- 

 merged protect their exposed leaves from transpiring 

 largely. 



There are details too numerous to mention in con- 

 nection with these coal-forming plants which go to prove 

 that there were large regions of swampy ground near 

 the sea where they were growing in a bright atmosphere 

 and uniform climate. Extensive areas of coal, and geo- 

 logical evidence of still more extensive deposits, show 

 that in Europe in the Coal Measure period there were 

 vast flats, so near the sea level that they were constantly 



1 A brackish swampy land is physiologically dry, as the plants cannot use the 

 water. See Warming's Oecology of Plants, English edition, for a detailed account 

 of such conditions. For a simple account see Slopes' The Study of Plant Life, p. 170. 



