TYPES OF FEEDING 23 



mushrooms and toadstools on a soil full of decomposing 

 organic matter, and you find mildews and moulds living on 

 jam or meat or cheese. But we have an exception to this 

 exception. There are certain bacteria which, being devoid of 

 chlorophyll, are fungi, and yet these can derive both their 

 nitrogen and their carbon from ammonium carbonate, so that, 

 like the green plants, they can live exclusively on inorganic 

 foodstuffs. 



Types of Feeding 



There are, in short, four types of feeding: 



I. HoLOPHYTic. This is the method of green plants, whose 

 food is inorganic, aqueous or gaseous. 



II. Saprophytic. Characteristic of fungi, plants devoid of 

 chlorophyll. Their food is organic and derived from dead 

 organic matter or the product of living organisms and is 

 absorbed in a liquid form. 



III. HoLOZOic. Peculiar to most animals. The food of 

 these is organic and is absorbed in the solid form. 



IV. Parasitic. This is a mode of feeding common to such 

 plants and animals as ingest organic food from some other 

 plant or animal, the host, in or on which they live. 



Plants have neither mouth nor stomach. They can absorb 

 their food nearly all over their body. Hence it is to their 

 interest to present as large an area as possible to the food- 

 stuffs that always are flowing around them. As is well known, 

 the average percentage composition of dry air is as follows: 



By volume By weight 

 Oxygen 2100 23-2 



Nitrogen 78-06 75-5 



Argon 0-94 1-3 



In addition there is rather more than 0-03 per cent, 

 of carbon dioxide by volume. 



It is in the interests of the plant to present the largest 

 surface to the air that it can. This is equally the case with 

 the roots which permeate in all directions the moist soil, 

 taking up water and the various salts dissolved in the water. 

 It is often said that the roots of a tree present to the soil a 



