spaces may be filled with water ; and unless the ground be properly 

 drained the soil becomes waterlogged, and it is common knowledge 

 to all of you that this is quite unfavourable for agricultural 01 

 horticultural purposes. The aeration or ventilation of the soil is to 

 a great extent provided by the burrowings of earthworms, insect 

 grubs, and other animals. 



THE WORK OF EARTHWORMS. 



I daresay some of you are acquainted with a work entitled "The 

 Formation of Vegetable Mould by Earthworms," written by Charles 

 Darwin and published as long ago as 1881. In that work he showed 

 the great importance of these lowly animals to the agriculturist both 

 in ventilating the soil and in improving its properties. Earthworms 

 swallow small quantities of soil in order to obtain decayed vegetable 

 matter occurring therein. This they do while making their burrows, 

 although they also feed en young fresh leaves. The small particles 

 are ground still smaller in the gizzard, which is like that of a fowl. 



("Reference was then made to the mode of action of earthworms ; 

 the formation and extent of their burrows ; to the astonishing num- 

 bers per acre, and the surprising amount of ''vegetable mould" 

 brought up by them to the surface annually, as estimated by Darwin 

 in England, by Urquhartt, and by 'Smith:}: in New Zealand.] 



This vegetable mould or "humus" differs from the subsoil in its 

 fine grain and dark colour, in its freedom from stones of a size 

 greater than can pass through the worm's digestive tract. It has 

 undergone certain changes while passing through the worm's body 

 and owes its dark colour to the presence of much organic matter, 

 that is, of decaying or decayed vegetable matter, and it contains 

 therefore an abundance of nitrogenous compounds. This "humus" 

 is alkaline, and affords energy to numerous micro-organisms which 

 convert it into simpler substances appropriate for plant nutrition. It 

 also improves the physical character of the soil. 



THE IMPORTANCE OF NITROGEN. 



I want now to direct your attention to the importance of nitrogen, 

 a gas which forms a considerable part of the air we breathe, but 

 which plants can take from the soil only in the form of nitrates. The 

 life both of animals and plants depends on the stock of nitrogen re- 

 tained in the soil in the form of nitrates. The total nitrogen in 

 arable soils is about 0.15 per cent ; higher in some soils than in others. 

 But the amount present as ammonia is only .0001 per cent., that is, 

 about one part in a million in arable soils, and about ten times as 

 much in heavily dunged soils. No soil constituents fluctuate more 

 than the nitrogenous. Plants remove them, rain drains them away. 



tUrquhart, A. T., "On the Habits of Earthworms in N.Z." Trans. N.Z. Inst., 

 vol. xvi., p. 266. 1884; and "On the Work of Earthworms," ibid, vol. xix., p. 

 119. 1887. 



JSmith, W. W., "Notes on N.Z. Earthworms." Trans. N.Z. Inst., vol. xix., 

 p. 123. 1887. (The names given by him to our earthworms are qi:.ite wrong, and 

 are corrected in next article). Smith, W. W., "Further Notes on N.Z. Earth- 

 worms," ibid, vol. xxv., p. Ill, 1893; and vol. xxvi., p. 155, 1894. 



