332 



ash; two witli the same sand and ash, but microbe-seeded with watery 

 extract for some plants from a ric-li garden soil, for hipines from a sandy 

 soil in which lupines were growing luxuriantly, and for some other 

 jjlants from soil where the particular plant was growing. In all, in 1889 

 and subsequently, they had grown in this way four descriptions of 

 annual plants, namely, peas, beans, vetches, and yellow lupines, and 

 four descriptions of longer-lived plants, namely, white clover, red clover, 

 sainfoin, andlucern. Without microbe-seeding there was neither nodule 

 formation nor any gain of nitrogen; but with microbe-seeding there was 

 nodule formation, and, coincidently, considerable gain of nitrogen. 



However, as in this exact quantitative series the plants were not 

 taken up until they were nearly ripe, it is obvious that the roots and 

 their nodules could not be examined during growth, but only at the con- 

 clusion, when it was to be supposed that the contents of the nodules would 

 be to a great extent exhausted. Another series wa« therefore under- 

 taken in which the same four annuals and the same four plants of longer 

 life were grown in specially made pots, so arranged that some of the 

 plants of each description could be taken up and their roots and nod- 

 ules studied at successive periods of growth; the annuals at three 

 l>eriods, (1) when active vegetation was well established, (-) when it 

 was supposed that the point of maximum accumulation had been 

 approximately reached, and (3) when nearly ripe; and the plants of longer 

 life at four periods, (1) at the end of the tirst year; (2) in the second 

 year, when active vegetation was reestablished; (3) when the point of 

 maximum acirumulation had been reached ; and (4) when the seed was 

 nearly rii)e. Each of the eight descriptions of plants was grown in sand 

 (with the i)lant ash) watered with the extract from a rich soil; also in 

 a mixture of two )»arts of lich garden soil and on«' part of sand. In 

 the sjind tlic infcition was comparatively loeal and limited, but some of 

 the nodules (le\eIoj(ed to a great size on the ro(»ts of tin' weak jdants 

 so grown. In the rich soil tin' infection was jiinch more general over 

 the whoh- area of the roots: the ikmIuIcs were much more numerous, 

 but generally \ cry much smaller. Ilventnally the nodules were i>icke<l 

 oft' tire roots, (•ounted, wt-ighed, and the dry substance and the nitro- 

 gen in them det«'rmined. 



Taking the peas as tvjucal of the annuals and the sainfoin of the 

 phHits of longer life, the general result was that at the thinl peri<nl of 

 growth of the ])eas in sand the amount of dry Tiiatter of the nodid«\s 

 was very nnu'h diminished, the percentage of nitrogen in the dry matter 

 was very nuu-h reduced, and the actual quantity of nitrogen remaining 

 in the total nodules was also very much reduced, in fact the nitrogen 

 of the nodules was almost exhausted. The peas grown in rich soil, 

 however, maintained much more vegetative activity at the conclusion, 

 and showed a very great increase in the nujid)er of nodules from the 

 first to the tliird ])eriod, and with this there w;is also nnu-h more dry 

 substance and even a greater actual quantity of nitrogen in the total 



