FOEMATION OF LEAPMOLD COVILLE. 341 



ments, are in all respects confirmatory of the theory that soil acidity 

 is one of the most influential factors in plant distribution and plant 

 ecology. 



The relation of leafmold to the existence of acid or nonacid soil 

 conditions may now be viewed with appreciative recognition. If the 

 conditions in any area are such that the decay of leaves follows 

 the uninterrupted course that leads to the formation of leafmold a 

 state of soil alkalinity is reached, with all the resultant effects on 

 the growth and distribution of the native vegetation. If, on the 

 other hand, the conditions are such that the course of decay is 

 diverted into the channel that ends in the formation of peat, a con- 

 dition of permanent acidity is indicated, with the accompaniment of 

 all those peculiar plant phenomena which are characteristic of such 

 a state. 



It is perhaps desirable to call attention here to the fact that while 

 partially decomposed vegetation appears to be the chief source of 

 soil acidity, there are mineral constituents of the soil, of wide dis- 

 tribution and great abundance, which are also acid in reaction. The 

 acidity of which we hear so much in agricultural writings as char- 

 acteristic of soils worn out by long years of careless farming is 

 doubtless due in large part to a natural mineral acidity unsheathed 

 by the removal of the lime that once neutralized it, for, like the 

 leaves of trees, many of the crops of agriculture are heavy with lime 

 and their uncompensated removal year after year has its inevitable 

 cumulative result. 



The speaker hopes that he does not overstep the proper bounds of 

 this address if he calls attention to conditions in bog deposits which 

 almost exactly parallel the two types of terrestial organic formation, 

 leafmold and upland peat. In bogs with alkaline waters, as, for 

 example, those underlain by marl, a condition of permanent acidity 

 is not maintained in the lower strata of the deposit. As far upward 

 as the alkaline waters penetrate, the antiseptic acids are not present, 

 decay continues, and the resulting formation is not peat, but a plastic 

 fine-grained black material that may best, perhaps, be designated by 

 that much misused term, muck. Muck corresponds in bog deposits to 

 leafmold in upland deposits, contrasting with bog peat as leafmold 

 contrasts with upland peat. 



We may follow this idea one step further. Coal is petrified peat. 

 As the purest peats are not formed in alkaline waters, it can not be 

 expected that the best coal will be found in situations indicative of 

 alkaline conditions. If coal is found immediately overlying beds of 

 marl or limestone it is to be expected that such coal will be of an 

 impure type, corresponding in origin to muck. The speaker takes 

 the liberty of suggesting to his geological friends that in reconstruct- 

 ing in theory the climatic and other conditions under which the 



