362 PALEOZOIC TIME. 



deducting 1-10 from the oxygen and making it nitrogen. Pure woody fibre and cellular 

 tissue (cellulose) consist of Carbon 44-44, hydrogen 6 - 17, oxygen 49-39 = 100; but, 

 through the presence of resinous and other matters, the average composition of wood is 

 as stated. The mean composition for the wood of three common species of Pines 

 (Pinus larix, P. abies, and P. picea) differs little from the average, it being (the nitrogen 

 included with the oxygen) Carbon 49 - 84, hydrogen 6*37, oxygen 43-75 = 100. From 

 Chevandier's various analyses (Ann. Ch. Phys., III. x. 129), the average constitution 

 of wood is, Carbon 51*21, hydrogen 0*21, oxygen 41*45, nitrogen 1*10 = 100. His re- 

 sult differs from the preceding, mainly in the separation of the nitrogen from the 

 oxygen. 



The ultimate analysis of Cork, on the preceding page, is by Mitscherlich. Cork (one 

 of the purest of barks) includes about ten per cent, of substances soluble in absolute 

 alcohol, one of which contains over eighty per cent, of carbon, with little oxygen, and 

 hence the low percentage of oxygen in the analysis of cork above cited. Bark also 

 contains, on an average, twelve per cent, of tannic acid (a compound of Carbon 52*4 per 

 cent., hydrogen 3*6, oxygen 44-0); and the rest of it is supposed to be impure cellulose. 



Dawson has suggested, in view of the many Sigillaria stumps hollowed out by decay, 

 and flattened stems of other trees, filled with shale or sandstone, found in the Coal- 

 measures, that the vegetable debris from which the coal has proceeded was largely bark, 

 or material of that general nature. But the occurrence of such stumps and stems outside 

 of the coal-beds, while proof that the interior wood of the plants was loose in texture and 

 very easily decayed, is no evidence that these trees contributed only their cortical portions 

 to the beds of vegetable debris. Moreover, the cortical part of Lepidodendrids (under 

 which group the Sigillarids are included by the best authorities) and of Ferns also, is 

 made of the bases of the fallen leaves, and is not like ordinary bark in constitution; and 

 Equiseta have nothing that even looks like bark. This cortical part was the firmest part 

 of the wood; and for this reason it could continue to stand, after the interior had decayed 

 away, — an event hardly possible in the case of a bark -covered Conifer, however decom- 

 posable the wood might be. Further, trunks of Conifers are often found in the later geo- 

 logical formations, changed, throughout the interior, completely to Brown coal or Lignite. 



Lycopods and Equiseta have, like Ferns and Mosses, the same constitution with ordi- 

 nary wood. The following are the results of analyses of species of these plants by Mr. 

 George W. Hawes, and also of a Sphagnum (Peat-swamp moss) by Websky, the ash 

 excluded : — 



1. Lycopodium dendroideum . 



2. Lycopodium complanatum 



3. Equisetum hyemale . 



4. Sphagnum 



As the Sphagnum is made of cellular tissue, the analyses show that, in Lycopods, the 

 cellular and vascular portions are essentially alike in constitution. 



The fact that the spores of Lycopods retain an amber-like color, in the coal, proves 

 that they do not yield to change so easity or thoroughly as the ordinary woody tissues, 

 but approximate in this respect to particles of resin. 



In the decomposition of wood and leaves in the air, the carbon 

 and hydrogen combine with oxygen, — both external oxygen and that 

 of the plant, — and the ultimate products are, as in the combustion 

 of wood, carbonic acid (CO 2 ) and water (H 2 0), with nothing left 

 behind. Thus it is, essentially, with the leaves and stems that fall 

 to the ground over the drier portions of the continent. 



When the vegetable material is under water, the atmospheric oxy- 

 gen is excluded, except the small part contained in water ; and this 

 oxygen, with some proceeding from the growing plants in the waters,, 



Carbon. 



Hydrogen. 



Oxygen. 



Nitrogen. 





48*70 



6*61 



43*25 



1*44 



Hawes. 



48*43 



6*61 



43-02 



1-94 



Hawes. 



47*50 



6*68 



44*49 



1-27 



Hawes. 



49*88 



6*54 



42-42 



1*16=100 



Websky 



