TJte Sources of the Nitrogen of our Leguminous Cro^s. 681 
In pot 3, also with soil-extract, and with two tall plants, the 
main roots extended to, and along, the bottom of the pot ; 
throwing off many side branches, with a very large quantity of 
fine fibrons root. The greatest distribution was, however, in the 
upper few inches of the soil. There were two clusters of nodules 
on one of the plants, and three on the other, besides smaller 
bunches. A large number of mostly single small nodules was 
also distributed along the roots. On one of the plants the 
largest cluster was on the main root, and on the other the 
clusters were on the side branches. 
j In pot 4, with the garden soil, and not higher plants, but 
' more vigorous and more matured growth than with soil-extract 
only, there was a dense mass of root-fibre throughout the first 
I six inches of depth. There were numerous nodules, the majority 
I single and within the upper two or three inches of soil. Tliere 
i were also a few small bunches. 
i Thus, then, the limited growth in pot 1, without soil-extract, 
' was coincident with the entire absence of nodule-formation ; 
and the increased growth in pots 2 and 3, with soil-extract, 
was coincident with a very great development of nodules. 
In pot 4, with garden soil, itself supplying abundance of 
nitrogen, there was also a considerable development of 
nodules, but distinctly less than in either pot 2 or pot 3, with 
soil-extract only. 
Losthj, vithovt soil-extract, and u-itliout nodules, tliere was no 
'/•'in of nitrogen; lnd,vnth soil-extract, and tcith nodule-fomiation, 
fJ'ere was ranch gain of nitrogen, tliere heing many times as miicli 
in the products of grovth as in the seed soxvn. 
The vetches were sown on July 10, two seeds being put into 
each pot; and the plants were takan up on October 26. The 
four pots of plants were photographed on August 3, August 20, 
September 27, and lastly on October 25, the day before being 
taken up. 
As with the peas, the plants in pots 2 and 3 with soil-extract 
had, before the end of July, shown more growth than those in 
pot 1 without it. Again, as with the peas, the vetches in the 
pure and sterilised sand showed extremely limited growth. On 
the other hand, those in pots 2 and 3, with the soil-extract, grew 
to a great height — indeed, higher than those in pot 4 with the 
garden soil. The heights of the plants were : in pot 1, without 
soil-extract, \\\ and 10^ inches; in pot 2, with soil-extract, 
52| and 67 inches ; in pot 3, also with soil-extract, 62^ and 51 
inches ; but in pot 4, with garden soil, only 53 and 36 inches. 
But, as in the case of the peas, whilst the plants in pot 4, with 
