700 T'he Sources of the Nitrogen of our Leguminous Crops. 
leguminous crops will be due to fixation under the conditions 
supposed, it is obvious that such a fact not only serves to explain 
the source of the hitherto unaccounted-for amount of the 
nitrogen of those crops themselves, but that it also affords an 
explanation of the source of the increased amount of nitrogen 
which other crops acquire, when they are grown in association 
or in alternation with Leguminosce. Lastly, the fact that herbace- 
ous leguminous plants (also papilionaceous shrubs and trees, as 
shown by Nobbe) are susceptible to the symbiosis, and under 
its influence may gain much nitrogen, serves to explain th6 
source of some, at least, of the large amount of combined 
nitrogen accumulated through ages in our soils and subsoils, 
and also the comparatively slow exhaustion of their stores of 
it, by cropping, drainage, and in other ways. 
Referring now to some of the more directly practical aspects 
of the subject, it may be observed that in Germany, Schultz, of 
Lupitz, has for some years farmed a considerable area of poor 
gravelly and sandy soil by growing leguminous crops — various 
clovers, lupins, serradella (Ornithopus sativus), &c., by means of 
kainit and pliosphatic manures, and he has found the land 
thereby very much enriched for future cereal and other crops. 
He finds, however, that it is necessary to vary the description 
of leguminous crop grown. In various parts of Germany, too, 
the system is gradually extending of growing lupins, serradella, 
or other leguminous crops, especially on poor sandy soils, with a 
view to their enrichment in nitrogen. And on a large estate in 
Hungary it was found that the results of the recent investiga- 
tions indicating the fixation of free nitrogen in the course of the 
development of leguminous crops were being carefully studied 
with a view to practical application. 
In our own country Mr. Mason, of E}Tisham Hall, Oxford- 
shire, commenced in 1889 some experiments with various 
Leguminosce on small plots; and in 1890 a considerable series 
in specially-built tanks or pits, in which he has growfi various 
leguminous agricultural plants, as well as some leguminous 
shrubs, with a view to the study of their root and nodule 
development, and the connection of these with luxuriance ot 
growth, and gain of nitrogen. He has also devoted about 200 
acres to the practical application of the recently acquired 
knowledge in regard to nitrogen fixation. Stated in a few 
words, his idea is, to reduce his area under roots, and to 
grow instead mixed crops of Jjeguminosa'. — beans, various 
clovers, &c. — liberally manured with basic slag and kainit, 
and to convert the produce in the first year into silage, and 
