98 MISSOURI STATE HORTICULTURAL SOCIETY. 



come to the surftice to eject their castings, and how thej" pull leaves, 

 twigs, seeds and germinating plants into their holes ; the leaves are 

 usually rolled singly and drawn by their stems down into the holes, 

 which extend almost vertically, frequently from three to six feet into 

 the soil. These vegetable substances are left several inches below the 

 surface, and when partially softened by decay, are eaten, forming, with 

 the organic matter of the earth, the main food supply of the worm. 



That earth worms play an important part in the economy of nature 

 is evident from the fact that they bring from underneath the ground 

 to the surface large quantities of earth in the shape of castings. These 

 casting are enriched by mixture with the intestinal and urinary secre- 

 tions of the worm, so that frequently sandy, poor soil, by this process, 

 is converted into a rich humus. Darwin has, by a long-continued 

 series of experiments in varioiis parts of England, calculated that on 

 each acre of ground more than two tons of dry earth annually passes 

 through the bodies of these worms and is brought to the surface, so 

 that the whole superficial bed of vegetable mould passes through their 

 bodies in the course of a very few years. 



The original surface of the earth was, in most places, solid rock, and 

 the present superficial layer of soil, varying in thickness from a few 

 inches to a hundred feet or more, has been formed by such agents as 

 the chemical and physical action of the atmosphere, water, acids, frost, 

 ice, wind, etc., while, in addition to these, the earthworm has played a 

 most important part, not only in enriching the soil, but in helping to 

 make it. Wind and rain tend to remove the surface soil from high 

 places and carry it to the the valleys below, so that there is a constant 

 tendency to lowering the country in height, and to a spreading out in 

 area near the sea shore. It is a fact, however, that in hardly any places 

 do we find the rocks entirely- denuded of their soil; consequently, there 

 must be some counteracting agency at work to assist in making, from 

 the underlying rock, new soil to replace that washed away by surface 

 drainage. It is here that the service of the earthworm is most marked; 

 their burrows, which are so numerous, provide an easy means of access 

 to the rocks for the atmospheric gases and organic acids which are the 

 chief causes of their disintegration. Mr. Julien states that there are 

 probably a dozen or more organic acids that are produced by the decay 

 of vegetable matter. Part of the intestinal juices of the earthworm 

 are acid, and it is probable, Darwin says, that they are the same as 

 those produced by the decay of organic matter. These acids, and the 

 acid salts produced by their combination with some of the alkaline 

 errths, act strongly in dissolving such common rocks as limestone and. 



