684 Tlie Sources of the Nitrogen of our Legiminous Crops, 
ment ; the main roots descended far down the deep pot almost 
vrithout brandling, but, at the bottom, a number of branches and 
a mass of root-fibre were produced ; the root-fibres were fleshy 
and succulent. No root-swellings or nodules were found. 
In pot 2, with the lupin soil-extract seeding, and luxuriant 
and maturing above-ground growth, there was, on the other 
hand, a veiy great development of root. Branches were thro^vn 
out throughout the whole length ; and at their ends masses of 
fleshy fibres were formed, which were thickly coated with root- 
hairs. On the main root of one plant, about three inches down, 
there was a large swelling or nodule the size of a field bean ; 
four inches lower there were three smaller ones on a side branch ; 
ten inches do\vn, there were three as large as peas ; and lower 
stiU, there was another small swelling, more like the nodules 
found on other plants. The other plant had less root growth. 
One and a half inch down there was a swelling the size of a small 
pea ; and between four and five inches lower there were three 
swellings, one as large as a bean, and the others about the size 
of a vetch seed. These swellings on the lupin roots, which were 
all on the main roots or thicker branches, were very different in 
appearance fi"om the nodules on the pea and vetch roots. They 
were, as desci'ibed, swellings, encasing the root where they grew. 
In pot 3, also with lupin soil- extract seeding, the plant 
which showed both gi-eat above-ground luxuriance and great 
seed-forming tendency, developed an immense amount of branch- 
ing root, with a great deal of root -fibre, which extended through- 
out the sand, but to a greater degree in the lower than in the 
upper half of the pot. The main root was woodv near the top. 
The lower root-fibres were fleshy and thickly coated with root- 
hairs. There were several swellings or nodules on the main 
root below 5 inches ; and lower down on a root branch there 
were several swellings ; there being in all twelve on this plant. 
The roots of the less luxuriant and less matured plant were 
smaller and more meagrely developed ; about 10 inches down 
there were two bunches of small nodules, and three single 
nodules ; and a little lower on a side branch another small 
nodule. 
With regard to the great development of the root-hairs on 
the fine fibrils of the roots of both pots 2 and 3, with quartz 
sand and soil-extract seeding, it may be supposed that this was 
an effort to acquire mineral nutriment, in quantity commensurate 
with the large amount of nitrogen fixed, and of nitrogenous 
nutriment so rendered available to the plant. 
In pot 1, with the lupin-soil itself, and less luxuriant above- 
ground growth, the distribution of root was also very different 
