A LITTLE AGRICULTURAL CHEMISTRY. 329 



During :i warm, dry day leayes also assume the sleeping po- 

 sition, which aids in checking evaporation. 



There are more '^ sleeping" plants among the Leguminosae 

 than are found in all other families put together. 



A Little A«:ricultural Ciiemistry. — Of the thirteen elements 

 necessary for plant growth the farnicr usually iieed take but little 

 care, except in the supj^ly of jiotassiiim. phosphorus and nitro- 

 gen, and of these three nitrogen is the most precious and costly 

 to obtain. All agricultural plants draw much of their food from 

 the atmosphere, and of those used by the farmer probably none 

 are much, if any. exceeded by clover in the large j^roportion of 

 nutriment thus derived. In this respect other leguminous crops 

 are much like reil clover. 



'*' Clover seed is the best manure that a farmer can use.'*' 

 Clover has l)een called •• a trap for niti'ogen/" as it collects and 

 presents large quantities of combined nitrogen in a form ready 

 to nourish growing crops. 



In the words of Dr. Kedzie: •'With an adequate supply of 

 combined nitrogen all the other chemicals of agriculture become 

 active, while a limited supply of active nitrogen correspondingly 

 limits the action of the rest. For high farming, or the raising 

 of exceptionally large crops, the great want is an abundant and 

 cheap supply of ammonia and the nitrates. 



"An acre of good clover will make 5,000 pounds of hay, con- 

 taining 2824^ pounds of mineral matter or ash. In this ash will 

 be 97t pounds of jootash, 96 pounds of lime, 34^ pounds of mag- 

 nesia, and 28 pounds of phosphoric acid. The hay will also con- 

 tain 108 pounds of cumbinetl nitrogen." ' 



The roots and stubble contain fully as much of these elements 

 as the hay. 



Baron J. B. Lawes found that in autumn, after tha last crop 

 of clover was cut, that remaining above ground, and to the depth 

 of 72 inches was examined : 



4:2 



