670 The Sources of the Kitrogen of our Leguminous Orops. 
Let us now consider what are the results obtained, when the 
conditions of growth involve neither sterilisation nor enclosure. 
The Vegetation Experiments in 1888. 
As already stated, it was in 1888 that the first of the recent 
experiments on the subject were made at Rothamsted. This 
preliminary series comprised experiments with peas, blue lupins, 
and yellow lupins. The peas were grown — 
Pot 1. In washed sand, with the ashes of the plant added ; 
but with no supply of combined nitrogen beyond a small deter- 
mined amount in the washed sand, and that in the seed sown. 
Pot 2. In similarly prepared saud, but microbe-seeded with 
25 c.c. of the turbid waterv extract from a rich garden soil. 
Pot 3. Duplicate of Xo. 2. 
Pot 4. In the rich srarden soil itself. 
Each of the two descriptions of lupins was grown — 
Pot 1. In sand prepared as for the peas, but with lapin- 
plant-ash instead of pea-plant-ash added. 
Pot 2. In similar washed sand, &c., but seeded with 25 c.c. 
of the turbid watery extract from a sandy soil where lupins had 
grown luxuriantly. 
Pot 3. In the lupin sandy soil itself. 
Pot 4. In rich garden soil. 
The twelve pots were arranged in a small greenhouse ; and 
distilled water, free from ammonia, was used for watering. 
The sand employed was a yellow sand from Flitwick, in 
Bedfordshire, such as is used bv gardeners in the neighbourhood 
for potting. The stones and coarser portions were removed by 
sifting, the remainder was several times washed, first with well- 
water, and afterwards with distilled ; then dried in a water-bath, 
and finally mixed with the plant-ash. It still contained 
0 00266 per cent, of nitrogen. 
The sandy soil from which the watery extract was made for 
microbe-seeding the pots where lupins were to grow, and which 
was used as the soil in experiment Xo. 3 with lupins, was ob- 
tained from land which had been reclaimed from a common in 
Suffolk^ on which no corn crop would grow, but on which, when 
subsequently sown with blue lupins, they grew as high as the 
hurdles. Excepting that visible organic matter was removed 
by sifting and picking, it was used as received, in which state 
it contained 0 0850 per cent, of nitrogen. 
The garden soil contained 10- 12 per cent, of moisture and 
0-3919 per cent, of nitrogen, corresponding to 0*4360 per cent, 
on the soil dried at 100= C. 
