Peas and Clover 139 
a degree of fertility to the soil that green plants can 
sustain life in it. Following upon that important 
addition to our knowledge of the production of 
nitrates in the soil, came the discoveries of the actual 
species that do the work, one having the power of 
producing nitrous acid, and another capable of turning 
that nitrous acid into nitric acid. To these insigni- 
ficant organisms is the fertility of our soils really due. 
But what, you may ask, has all this to do with 
Peas and Clover? Everything: Peas and Clover 
could not provide the animal world with their valu- 
able flesh-forming seeds but for these nitrifying 
bacteria—neither, indeed, could any of the ordinary 
farm crops be produced. 
Most people who have grown Scarlet Runners, and 
have pulled up the roots after the frosts have cut 
down the stems, have noticed how these roots are all 
distorted and gouty in appearance. Similar nodules 
may be found on the roots of Sain-foin, Clovers, ete., 
and it is now found that these tubercles contain a 
great quantity of nitrogen and swarm with bacteria. 
The explanation, then, of leguminous plants con- 
taining more nitrogen than was in the soil appears to 
be that they take in the free nitrogen of the atmosphere 
and convey it to the roots, where the action of the 
bacteria converts it into such form (nitric acid) that 
the plant can assimilate it. It appears probable that 
each type or genus of leguminous plants has its own 
special bacteria. 
Having thus briefly indicated a remarkable 
character of this group, let us look at the stem, 
leaves, and flowers. The most widely distributed of 
our native Peas is the Meadow Vetchling (Lathyrus 
