PROCEEDINGS OF THE COTTESWOLD CLUB I05 



experiments in which nitrogeneous manures were used were 

 what Priestley used to call "bad experiments;" they 

 showed varying results and thus proved nothing. 



Where the plants experimented with were Cereals 

 (Gramineae) a correspondence w^as found to exist between 

 the amount of Nitrogen supplied in the manure and the 

 amount absorbed by the plant, but where the plants experi- 

 mented with were Leguminosae no such correspondence 

 appeared to exist. 



Already as early as the year 1862, Red Clover had 

 been observed to flourish without any Nitrogen at all; but 

 in other years, under apparently precisely similar con- 

 ditions, all the plants had died. 



Again and again the repeated experiments failed to show 

 any relation either between the Nitrogen supplied as 

 manures or between the Nitrogen in the soil and that in 

 the dried plant. 



The failure of these experiments led Hellriegel and 

 Wilfarth to the determination to institute a careful and 

 prolonged enquiry into this separate question of the 

 behaviour of both Gramineous and Leguminous plants in 

 relation to Nitrogen, which their preliminary experiments 

 had so clearly shown to exhibit varying phenomena 

 hitherto unexplained. The complexity of the factors to 

 be controlled renders such an experiment one of great 

 care and labour. The soil and its quality, the amount of 

 light and heat, the degree of humidity and temperature of 

 the air by which the plants are to be surrounded, and kept 

 in as nearly as possible natural conditions, as well as a 

 complete command of the food they are to have, are 

 among the chief of these factors. 



As various methods of securing the desirable conditions 

 were tried and found capable of improvement, or highly 

 suitable, the years led on to 1873, when Hellriegel 

 published some preliminary record of the results already 

 achieved in a work, "Beitriige zu den naturwissenschaftlichen 

 Grundlage des Ackerbaus." 



