682 The Sources of the Nitrogen of our Leguminous Crops. 
the garden soil, flowered and seeded, those in pots 2 and 3, with 
the soil-extract only, did not, but continued to vegetate, extend- 
ing upwards, the higher and newer portions apparently at the 
expense of the lower and older parts of the plant. 
In pot 1, without soil-extract, and with very limited above- 
ground growth, there was much less development of root than 
in either pot 2 or pot 3 with soil-extract, or than in pot 4 with 
the garden soil. The main roots descended to the bottom oi 
the pot, and threw out a number of side branches, but there was 
a marked deficiency of root-fibre ; and not a single nodule was 
formed. 
In pot 2, with soil-extract seeding, and very extended above- 
ground growth, there was a dense mass of root and root-fibre, 
which distributed throughout the pot, though the greatest 
accumulation was within the first three inches of depth. There 
were numerous nodules, but considerably less in quantity than 
on the corresponding pea roots. They were mostly single, and 
the greater number were found in the lower layers, which is also 
contraiy to the result with the peas. They were, moreover, 
generally exceedingly small. 
In pot 3, also with soil-extract, and with very extended 
above-ground growth, there was also an immense development 
of root and root-fibre, through the whole area of the sand ; the 
greatest accumulation being in the upper and lower portions of 
the pot, with less in the middle. There were again many 
nodules, but very small, and probably fewer than on the roots 
in pot 2. All the nodules were single, and fairly distributed 
over the whole root area. 
In pot 4, with garden soil, and as with the peas, less extended 
but more vigorous and more matured growth than in sand with 
soil-extract only, there was" a moderate amount of root and of 
root-fibre, chiefly within the upper six inches of depth ; but 
there was altogether very much less of root development than in 
either pot 2 or pot 3, with the sand and soil-extract. There were 
many nodules, but all single and very small ; and they appeared 
to be flattened, as if exhausted of their contents. 
Here, then, with the vetches, as with the peas, the very re- 
stricted above-ground growth in pot 1, without soil-extract 
seeding, was associated with very limited root development, and 
with the entire absence of nodule-formation. On the other 
hand, the greatly extended vegetative growth in pots 2 and 3, 
with soil-extract, was associated with an immense development 
of root and root-fibre, and with the formation of numerous 
nodules. Again, in the garden soil, with its liberal supply of 
combined nitrogen, there was much less development of roots, 
