MANURES 107 



strawberries, etc., and there is one consideration which seems 

 to negative such a suggestion ; for the two series of experiments 

 with gooseberries are remarkably concordant in the general tenor 

 of their results (see p. 96), although the soil in which they were 

 made was very different in character; that in which the first 

 series was made was, for the most part, sandy, and that used for 

 the second series was clayey, containing, moreover, more than 

 double the proportion of food-constituents than the former did. 

 The composition of the two soils may be contrasted thus 



and it is extremely improbable that in two such very different 

 soils the physical alteration produced by dung would have 

 had such a closely similar effect on the behaviour of the 

 bushes. 



The extraordinary action of dung in this case suggested at 

 first that it might be due to the presence in it of what have been 

 termed auximones, that is, substances which are not in them- 

 selves nutrients, but which, by their presence, even in minute 

 quantities, render the plants capable of absorbing such nutrients 

 as are present. The results, however, hardly favour this explana- 

 tion, for the yield of fruit is more or less proportional to the 

 dressing applied. Yet it is a point which calls for further 

 investigation. The more probable explanation at present is 

 that dung contains its nutrients particularly the nitrogenous 

 nutrients in a form which is specially suited to the requirements 

 of gooseberries, though comparatively inefficient in the case 

 of apples, etc. Such a conclusion indicates how much we 

 have still to learn as to the physiological differences between 

 plants. 



It is highly suggestive that this is not the only instance in 

 which gooseberries, and probably other bushes, 'show a radical 

 difference in behaviour from apples, etc. ; such differences have 

 also been noticed in the results of trenching the soil (p. 29) and 

 of root-injury on planting (pp. 35, 54). 



One of the most important teachings of the Woburn manurial 

 results, especially as regards apples, is to emphasise the view 



