SAPROPHYTES 139 



ing results, it may be said that the wheat plot points to the fact that 

 where the soil is in good condition, through the application of farm- 

 yard manure, the artificials that may be most profitably applied are 

 lime (4 parts), superphosphate (3 parts), and sulphate of ammonia 

 (1 part). On the other hand, where the land is not in such high 

 condition, this dressing should be supplemented by a dressing of 

 potash salt. The analyses show that by the application of these 

 dressings the value and quality of the crop are increased because 

 the operations of the nitrifying organisms have been thus favoured. 



4. The Saprophytie Bacteria in Soil 



This group of micro-organisms is by far the most abundant 

 as regards number. They live on the dead organic matter of the 

 soil, and their function appears to be to break it down into simpler 

 constitution. Specialisation is probably progressing among them, 

 for their name is legion, and the struggle for existence keen. After 

 we have eliminated the economic bacteria, most of which are obviously 

 saprophytes, the group is greatly reduced. It is also needless to add 

 that of the remnant little beyond morphology is known, for as their 

 function is learned they are classified otherwise. It is probable, as 

 suggested, that many of the species of common saprophytes normally 

 existent in the soil act as auxiliary agents to denitrification and 

 putrefaction. At present we fear they are disregarded in equal 

 measure, and for the same reasons, as the common water bacteria. 

 An excess of either, in soil or water, is not of itself injurious as far 

 as we know ; indeed, it is probably just the reverse. It is, however, 

 frequently an index of value as to the amount and sometimes con- 

 dition of the contained organic matter. The remarks made when 

 considering water bacteria apply here also, viz., that an excess of 

 saprophytes acts not only as index of increase of organic matter, 

 but as at first auxiliary, and then detrimental, to pathogenic organisms. 

 It will require accurate knowledge of soil bacteria generally to be 

 able to say which saprophytic germs, if any, have no definite function 

 beyond their own existence. It may be doubted whether the stern 

 behests of nature permit of such organisms. However that may be, 

 we may feel confident, though at present there are many common 

 bacteria in soil, as also in water, the life object of which is not 

 ascertained, that as knowledge increases and becomes more accurate, 

 this special provisional group will become gradually absorbed into 

 other groups having a part in the economy of nature, or in the 

 production of disease. At present the decomposition, denitrifying, 

 nitrifying,* and nitrogen-fixing organisms are the only saprophytes 



* It has already been pointed out that the nitrifying bacteria, though able to 

 live on organic matter, do not require such either for existence or for the performance 

 of their function. 



