FIXATION OF FKEE NITKOGEN. 145 



used, which was washed and sterilised by heat. The ash of 

 the plant and a small quantity of calcium-carbonate were 

 added. 



There were four pots of each description of plant, excepting 

 in the case of the white clover, of which there were five. For 

 the peas, vetches, beans, white clover, red clover, sainfoin, and 

 lucerne — No. 1 was with the prepared quartz sand without 

 soil-extract; Nos. 2 and 3 were with the quartz sand and 

 garden-soil extract added ; and No. 4 was with the garden- 

 soil itself; the fifth pot of white clover receiving calcium- 

 nitrate instead of soil-extract. Of the lupins (both blue and 

 yellow) — No. 1 was with the prepared quartz sand without 

 soil-extract ; Nos. 2 and 3 were with lupin-soil extract added ; 

 and No. 4 was with the lupin sandy soil itself, to which 0.01 

 per cent of the plant ash was added. 



The analytical details relating to the experiments com- 

 menced in 1889, and subsequently, though now completed, 

 have not yet been published, so that numerical results cannot 

 be given here. The following general statement of their bear- 

 ing will, however, convey a clear idea of their significance 

 and their importance. 



First as to the peas. There was limited growth in pot 1, Fig. 3 ex- 

 with sand without soil - extract, and there was an entire l >lained - 

 absence of nodule - formation on the roots. The increased 

 growth in pots 2 and 3, with soil-extract, was coincident with 

 a very great development of nodules. In pot 4, with garden- 

 soil, itself supplying abundance of combined nitrogen, and 

 doubtless micro-organisms as well, there was also a consider- 

 able development of nodules, but distinctly less than in either 

 pot 2 or pot 3 with sand and soil -extract only. Lastly, 

 without soil-extract, and without nodules, there was no gain 

 of nitrogen ; but with soil-extract, and with nodule-formation, 

 there was much gain of nitrogen ; there being many times as 

 much in the products of growth as in the seed sown. For 

 illustrations of the above-ground growth, see fig. 3. 



With the vetches, as with the peas, there was very restricted Fig. 4 ex- 

 above-ground growth in pot 1 without soil-extract seeding, P lained - 

 and this was associated with very limited root-development, 

 and with the entire absence of nodule-formation. On the 

 other hand, the greatly extended vegetative growth in pots 2 

 and 3 with soil -extract was associated with an immense 

 development of root and root-fibre, and with the formation of 

 numerous nodules. Again, in the garden-soil, with its liberal 

 supply of combined nitrogen as well as micro - organisms, 

 there was much less development of roots, and less also of 

 nodules, than in the pots with sand and soil-extract only. 

 Further, without microbe-seeding, and with no nodules, there 



VOL. VII. K 



