678 The Sources of the Nitrogen of our Leguminous Crops. 
the last two columns. The first of these shows the relation of 
the amount of nitrogen in the total products (soil and j^lants 
together) to the total initial nitrogen (soil and seed together), 
taken as 1. Even in pot 1, with the impure and not sterilised 
sand, but without soil-extract, there was, so reckoned, more 
than three times as much nitrogen in the products as in the 
soil and seed; in pot 2, with soil-extract seeding, there was 
nearly five times as much ; and in pot 3, also with soil-extract, 
there was more than four times as much. In the case of pot 4, 
however, with garden soil, owing to the large amount of initial 
nitrogen in the soil, the gain, though actually large, appears 
when so reckoned lout small. 
It is in the last column of the Table, in which, disregarding 
the nitrogen in the soils, which was so nearly the same at the 
beginning and at the end, and reckoning the relation of the 
nitrogen in the total products of growth to that in the seed taken 
as 1, that the large amount of fixation is clearly brought to 
view. So reckoned, the nitrogen in the substance gi'own to 
that in the seed sown was : in pot 1, 9^-fold ; in pot 2, nearly 
18-fold; in pot 3 nearly lo-foid ; and in pot 4, nearly 22- 
fold. 
Here, then, under non-sterilised conditions — in fact, with suit' 
able microhe-infeciion of the soil — there v:as very considerable 
fixation of free nitrogen. 
TJie Vegetation Experiments in 1889, 1890, and 1891. 
Since 1888 more extensive series of experiments have been 
made, on substantially the same lines as those already described. 
In 1889 peas, vetches, blue lupins, yellow lupins, red clover, 
and lucerne were sown ; and in 1890 beans, white clover, and 
sainfoin. Excluding the blue lupins, which failed, it will be 
seen that the series included experiments with four annuals, 
namely, peas, vetches, beans, and yellow lupins ; also with four 
plants of longer life, namely, white clover, red clover, sainfoin, 
and lucerne. And, as will be seen further on, experiments 
with the same four annuals, and the same four plants of longer 
life, were commenced in 1890, of which some are still in pro- 
gress, on somewhat different lines from those above referred to, 
with a view to the investigation of some points of importance, 
which the necessary conditions of growth and subsequent treat- 
ment of the plants in the glass-house did not admit of. 
Referring to the experimeots in the glass-house, it may be 
stated that for the lupins, the sainfoin, and the lucerne, specially- 
made pots of glazed earthenware were employed. They were 
