144 



THE GEOLOGICAL HISTORY OF PLANTS. 



"This difference is not less striking when we reduce 

 the above centesimal analyses to correspond with the 

 formula of cellulose, C24H20O20, and represent cork and 

 Lycopodium as containing twenty-four equivalents of 

 carbon. For comparison I give the composition of speci- 

 mens of peat, brown coal, lignite, and bituminous coal :* 



Cellulose CaiHaoOjo 



Cork C^iH.efffOeTL- 



Lycopodium Cs4Hi8AN0si% 



Peat (Vaux) C24Hi4i%Oio 



Brown coal (Schrother) GiiBLK^Oarxis 



Lignite (Vaux) Cs4Hii^OoiV 



Bituminous coal (Regnault) C24HioOs-i% 



"It will be seen from this comparison that, in ulti- 

 mate composition, cork and Lycopodium are nearer to 

 lignite than to woody fibre, and may be converted into 

 coal with far less loss of carbon and hydrogen than the 

 latter. They in fact approach closer in composition to 

 resins and fats than to wood, and, moreover, like those 

 substances repel water, with which they are not easily 

 moistened, and thus are able to resist those atmospheric 

 iniiuences which effect the decay of woody tissue." 



I would add to this only one further consideration. 

 The nitrogen present in the Lycopodium spores, no doubt, 

 belongs to the protoplasm contained in them, a substance 

 which would soon perish by decay ; and subtracting this, 

 the cell- walls of the spores and the walls of the spore- 



* " Canadian Naturalist," vi., 253. 



