For the Layman 



farmyard manure — a compost of straw. This artificial farm- 

 yard manure is not artificial in the sense that many purely 

 inorganic fertilizers are. It derives nothing from large live- 

 stock, but is nevertheless a biological product, because many 

 forms of living micro-organisms take part in the rotting. 

 Artificial farmyard manure ("Adco" manure) has been shown 

 to be the equal of farmyard manure as far as crop-producing 

 capacity is concerned. It looks, therefore, as though the 

 biological contribution to fertility is much the same, whether 

 it is supplied by a few large animals or by a multitude of small 

 forms of life. 



It is too much to say that the auxins in plants, or growth- 

 substances in general, are the very stuff of life, but the con- 

 nexion between plant-growth and the natural growth-sub- 

 stances is so intimate that it is tempting to suggest that since 

 the discovery of the modes of action of growth-substances we 

 are a step nearer understanding the mechanism of life itself. 



One paragraph more. Once Kogl had found the crystals 

 that turned out to be indole-acetic acid, it was easy, by means 

 of a few comparatively simple chemical tests, to say what the 

 substance was. This was because a great deal was already 

 known about the chemical relationships of indole-acetic acid. 

 The chemistry of indole-acetic acid and of its relatives had 

 been worked out over many years by researchers who were 

 mainly interested in pure, or theoretical — as distinct from 

 applied — chemistry; that is, many of these chemists were 

 interested in chemistry for its own sake. They suspected little 

 of the future importance of their work, but they were broaden- 

 ing knowledge, though, at the time their work was done, 

 a good deal of it must have seemed to have no practical value 

 except, possibly, as an exercise in chemistry. We benefit 

 to-day from the results of the work of these people who laid 

 the foundations of chemistry many years ago. A similar 

 remark would be true of the work of scientists in other fields 

 besides chemistry. That is the reason why I selected as the 

 keynote of this book the proverb that appears on the title- 

 page. 



