112 MASSACHUSETTS HORTICULTURAL SOCIETY. 



plants, and of others as lime plants. Indeed special manuring, as 

 In the use of superphosphate of lime for the turnip crop has been 

 generally practised in Great Britain for a quarter of a century at 

 least. 



Knowing what elements plants must derive from the soil, it was 

 natural enough that chemists- should attempt, by an analysis of the 

 soil, to ascertain whether those elements exist in the soil in pro- 

 portions sufficient to nourish the proposed crop. About twenty- 

 five years ago, in this country, the anal3^sis of soils for this pur- 

 pose, was advocated by Prof. Mapes, Dr. Lee, and others, as a 

 safe practical method of ascertaining what fertilizers were neces- 

 sary to be applied for a given crop. 



In this direction, chemical science soon found a limitation, as 

 applied to practical agriculture. As an illustration, it was found 

 by actual analysis that a rich soil from the Scioto Valley, was 

 apparently no more fertile than a sterile soil from Massachusetts. 

 The chemist in his laboratory could extract in a single hour from 

 a granite pebble, or from sand, more potash than a plant could ex- 

 tract in a hundred years. It was soon found that, aside from the 

 practical difficulty of procuring for the chemist a fair specimen of 

 a field or a farm, it was necessary not only to consider the physical 

 condition of the soil, but also the condition, chemical or other- 

 wise, in which the fertilizing elements exist. 



Equivalents in the chemical laboratory are found not to be always 

 equivalents as fertilizing agents. It seems to be generally con- 

 ceded that the mineral phosphates of lime, although by chemical 

 tests thej' appear to possess the same elements of plant food as the 

 animal phosphates found in bone, yet do not produce the same 

 valuable eff"ects upon our crops. 



A theory advocated by Prof. Mapes, and supported by some 

 French chemists, is interesting in this connection. It is called 

 " The Progression of Primaries," and is based upon the idea that 

 the elements of plant food increase in value as they progress from 

 the mineral through the vegetable and the animal kingdom. The 

 particle of lime or potassa that is found in the rock is taken up by 

 some plant and becomes part of it. It is then devoured b}^ some 

 animal and becomes a part of the animal, and by and by returns 

 by decomposition to the soil. Having been thus many times 

 assimilated into the higher forms of life, it becomes better fitted 

 for its future round of service, and enters more readily into the 



