674 Tlie Sources of the Nitrogen of our Leguminous Crops. 
plants, for, as ^1 be seen, the differences in these respects are 
verr great with different descriptions of plant, and under the 
different conditions of grovvth. 
The roots of the peas in pot 1 , with the washed and dried, bat 
not sterilised, yellow sand, showed a densely matted mass of fibre, 
by far the greater portion of which was accumulated within the 
top four inches ; and. notwithstanding there was no soil-extract 
seeding, there were many nodules on the roots, but fewer, and 
generally much smaller, than on those grown with the soil- 
extract seeding. They were also less characteristically ac- 
cumulated near the surface, and more distributed along the 
root fibres. There were, however, some agglomerations of 
nodules. Comparing this result with that obtained in 1889, with 
a purer and sterilised sand, in which case there were no nodules, 
there can be little doubt that the development of nodules, and 
the fairly luxuriant growth in this pot without soil-extract 
seeding, are to be attributed to the impurity and non-steril- 
isation of the sand. 
The roots in pot 2. with soil-extract seeding, also showed a 
dense mass of fibre, which, however, extended from the top to 
the bottom of the sand, penetrated the layer of flints, and 
distributed over the bottom of the pot. The roots were, in fact, 
much more generally distributed and less accumulated within 
the surface layers than in pot 1. The most developed root had 
three large agglomerated nodules, each with some scores of 
protuberances, somewhat as on a raspberry or mulberry. The 
other plants also showed similar nodules, but of a smaller size. 
There were also a number of small clusters distributed over the 
rootlets, but very few single nodules, differing in this respect 
from the development observed in pot 1. 
In pot 3, also with soil-extract seeding, each of the three 
plants developed a mass of root-fibre extending throughout the 
sand, but less near the bottom. There were large agglomerations 
of nodules on the roots of each plant. There were, besides, 
many small clusters, and here and there single nodules. By 
far the most of the nodules were within the top three ihches of 
the sand, but one considerable bunch was found as low as four 
inches from the surface. As in the other cases, the nodules 
were grey, and much lighter in colour than the roots on which 
they grew. 
Each of the three plants in pot i, with the garden soil, had 
a stouter main root than any of those in the other pots. From 
the side branches there proceeded a large amount of fine root- 
fibres which extended throughout the whole soil, those from the 
different plants being much interwoven. The roots extended 
round the sides and along the bottom of the pot, much more 
