No. 443-] 



ORGANIC REMAINS. 



7*7 



of an excess of water, humic acid and certain hydro-carbons are 

 formed, and it is to these substances the said deposits owe their 

 anti-septic properties, which make it possible tor organic remains 

 to resist decay for a sufficiently long time to allow deposition of 

 the sediment, in which they are finally imbedded. 



Trees tailing into the water, branches, roots, leaves, seeds, 

 and other parts of plants are often in this way preserved, and 

 retain sometimes their shape, color and anatomical structure to 

 a surprising degree, so that there is no difficulty in discriminating 

 the distinct species. It is, however, only lignihed and corky 

 tissues that are able to resist decomposing. All those organs 

 which have not cell-walls modified in this way, are liable to be 

 destroyed. Of leaves, for instance, only the epidermis and vas- 

 cular bundles remain, while mesophyll and similar tissues decay. 



The fossil remains are therefore often quite different in 

 appearance Horn the plants that fell into the water, where they 



L.^nd .S\ l^ unaltered, both with regard to 



