114 PROCEEDINGS OF THE COTTESWOLD CLUB 



would contain certain micro-organisms natural to the soil, 

 and in watering pots with this solution an inoculation of 

 the pot would take place. The result of these two years 

 experiments was no less remarkable than those of 1883 — 

 1885. 



In the perfectly sterilized pots the behaviour of the 

 Cereals and Leguminosse was the same. 



In the case of oats and maize no appreciable increase of 

 growth took place even in the watered pots, but in the 

 case of the Leguminosse the addition of the soil extract 

 invariably stimulated the growth of the plants, and a large 

 absorption and assimilation of Nitrogen took place, 

 evidenced by the subsequent analysis of all parts of the 

 plants. Furthermore, the formation of tubercules on the 

 roots of the plants proceeded pari passu with the supply 

 of soil extract. No tubercules were formed where sterile 

 conditions prevailed, and where Nitrogen was supplied, 

 [but under sterilized conditions] the same result appeared. 

 Hellriegel felt justified in communicating to the German 

 Association in 1887 that the " tuberosities were in direct 

 relation with the assimilation of Nitrogen." 



The " period of inanition," exhibited by the earlier 

 experiments was explained satisfactorily by the new facts, 

 for supposing a soil containing no Nitrogen to hold a few 

 living micro-organisms, capable of entering into symbiosis 

 with the plant roots — some time must elapse before they 

 could be sufficiently developed to set up the chemical 

 action now demonstrated. 



Such is but a bare and meagre outline of the labours 

 which have been so fruitful in physiological advances of 

 the highest importance. A study of the original papers 

 of Hellriegel and Wilfarth can alone convey a notion of 

 the multitude of laborious analyses by which these 

 results have been arrived at. It should be noted too that 

 subsequent investigations by other workers in the same 

 field, by (principally) Schloesing and Laurent, and by 



