The Smirces of the Nitror/en of our Leguminous Crops. 689 
than broad, sometimes single, but more often divided or 
branched, there being generally two or three, and sometimes as 
manv as twenty, or even many more, in a bunch, joined at the 
base. They have, so far, not been observed on the main root, 
but onlv on the root-fibres, and less near the surface than 
within the I'ange of the subsoil. In some cases such a tuft or 
bunch will be at the end of a fine fibre, by which it is connected 
with the main root. As the season advances these bodies become 
shrivelled, and are in fact empty shells. 
Among the Le<iuininos(e growing in the mixed herbage of 
grass land in 1868 nodules were observed on the root-fibres of 
Lathynis pratensis, especially near the surface of the soil ; on 
the ultimate root-fibres of Trifolium p-ratense ; and on the smaller 
rootlets of Trifolium repens. 
In the case of red clover growing in rotation on arable land, 
an abundance of nodules has been found, both near the surface 
and at a considerable depth. They are generally more or less 
globular or oval. Some found on the main roots were more 
like '• swellings than attached tubercles, not, however, encasing 
the root, but only on one side. The greater number are, how- 
ever, small and distributed chiefly on the root-fibres. Again, 
on the plot of rich garden soil on which red clover has now been 
grown at Rothamsted for thirty-eight years in succession, veiy 
numerous nodules, chiefly globular and small, have been found 
on the roots — for the most part within the first few inches of 
soil, but some to the depth of a foot or more, diminishing, how- 
ever, very much both in number and in size as the clayey subsoil 
was reached. 
Obviously much more evidence than the foregoing few 
observations can supply is needed in regard to any difterence 
in chai-acter, or relative prevalence, at diflerent periods in the 
life and growth of the plant, and under different conditions of 
soil, both so far as mechanical state and porosity, and richness 
or otherwise in available supplies of combined nitrogen are con- 
cerned, before any clear conception can be attained of the 
connection between nodule-formation, luxuriance of growth, and 
gain of nitrogen. The subject in various aspects is being 
fuiiher investigated at Rothamsted, and some of the results so 
far obtained will be briefly referred to farther on. 
How IS THE FlXATION OF NlTROGE s TO BE EXPLAINED ? 
Reviewing the whole of the resulls which have been brought 
forward, there can be no doubt that the fact of the fixation of 
free nitrogen in the growth of Leijuminosce under the influence 
VOL. n. T. s.— 8 z / 
