PROGRESS IN AGRICULTURAL SCIENCE. 493 



There was a considerable development of roots in the upper 

 part of pot 1, and a number of root-tubercles were formed, owing 

 to the fact, as proved by subsequent experiments, that the sand 

 was not sterilized before planting the peas. The roots in pots 2 

 and 3, inoculated with soil-extract, were more abundant than in 

 pot 1, and the root-tubercles were decidedly more numerous and 

 frequently in clusters. The above-ground growth was more lux- 

 uriant in pots 2 and 3 than in pot 1, and " in the total vegetable 

 matter there was in pot 2 more than twice, and in pot 3 nearly 

 twice as much, nitrogen as in pot 1 without soil-extract." 



A comparison of the total nitrogen in the soil and plants at the 

 close of the experiment with the original nitrogen in the soil and 

 seeds showed that " in pot 1, with the impure and not sterilized 

 sand, but without soil-extract, there was more than three times as 

 much nitrogen in the products as in the soil and seed ; in pot 2, 

 with soil-extract, there was about five times as much ; and in pot 

 3, also with soil-extract, there was more than four times as much." 

 There was very little difference in the amount of nitrogen in the 

 soils at the beginning and the close of the experiments, and, neg- 

 lecting this, it appears that " the nitrogen in the substance grown 

 was, in pot 1, nine and one half-fold ; in pot 2, nearly eighteen- 

 fold ; and in pot 3, nearly fifteen-fold that supplied in the seed." 



In 1889 similar experiments were made with peas, red clover, 

 vetches, blue lupines, yellow lupines, and lucern. For the lupines 

 and lucern glazed earthenware pots, six inches in diameter and 

 fifteen inches deep, were provided, and for the other plants the 

 same pots were used as in 1888. 



" The sand used was a rather coarse white quartz sand, from 

 which the coarser and the finer portions were removed by sifting, 

 and more of the finer by washing and decantation, first in well, 

 and afterward in distilled water. 



"In each case the sand was mixed with 0*1 per cent of the 

 plant-ash, and 0"1 per cent of calcium carbonate." The prepared 

 sand was sterilized by keeping it for several days at a temperature 

 of nearly 100 C. in a water-bath. 



" There were four pots of each description of plant." Of the 

 peas, clover, vetches, and lucern there was one pot of each of the 

 prepared quartz sand without inoculation with soil-extract ; two 

 pots of the prepared quartz sand inoculated with the microbes of 

 a garden-soil extract ; and one pot of garden soil itself. Of the 

 blue and the yellow lupines there was one pot of each of the pre- 

 pared, but not inoculated, quartz sand ; two pots of the prepared 

 quartz sand inoculated with an extract of a soil from a field where 

 lupines were growing; and one pot of the lupine soil itself, to which 

 was added 0*01 per cent of lupine plant-ash. 



"The soil-extracts were in all cases added on July 9th, before 



