THE GREATER BIRD’S-FOOT TREFOIL— continued. 
Names.” The much larger L. tiliginosus Schkuhr, which, as its specific name (from 
the Latin uUgo, marshiness) indicates, inhabits wet places, has not, perhaps, been 
popularly distinguished, and has accordingly no distinctive English popular names 
of its own. Being, however, a perennial, with an elongated, branched, and sucker- 
bearing rhizome, it is known in Guernsey as Grand RHe-beuf^ a name transferred from 
the Rest-harrow. It may straggle among rushes, or other water-side vegetation, to 
a height of two or three feet ; and it bears, on long peduncles, clusters of from five 
to twelve flowers, with calyx-teeth all spreading and divergent from the bud stage. 
Our Plate shows the tubercles on the roots which are so important a feature 
among Leguminosce. In a recent little book entitled “ Plant Life,” Professor J. B. 
Farmer gives the following lucid explanation of these structures : — 
‘^Thesc swellings are due to luxurious growth of ihe tissues of the cortex or rind. Examined microscopically the cells 
are found to contain enormous numbers of bacteria-like organisms to which the name of Bacillus radicola has been given. 
“The root becomes infected by this bacillus from the soil, in ordinary samples of which it is apparently always present. 
The bacillus enters through a root-hair, and when it reaches the interior of the cortex it multiplies there, producing the nodular 
outgrowths in question. It feeds and grows mainly at the expense of the sugars and other substances supplied by the host* 
plant, these having, of course, been produced as the result of the photosynthetic activity of its leaves. 
“ But when thus provided with carbohydrate food, the bacillus is able to manufacture the essential nitrogenous compounds 
necessary for the production of protoplasm by utilising the free nitrogen of the air. Most plants have to take in their nitrogen 
in a combined form, as ammonia salts, nitrates, etc,, for nitrogen is a very inert element, and difficult to force into combination 
with others. Bacillus radicola is one of the very few organisms which can perform this really stupendous task, provided that it is 
supplied with the means of obtaining the energy required for the process in the form of appropriate carbohydrate nutrition. . , 
After the bacilli have thriven for a while, mainly at the expense of the food supplied by the root in which they are living and 
multiplying, a change comes over them. Many of the individuals become weaker, and undergo a sort of degeneration, whilst a 
few pass into a resting stage in which they become highly resistant to adverse conditions of life. The leguminous plant, which 
hitherto has been paying out carbohydrate food to the bacillus, now begins to receive, and the harvest is a rich one, for it 
acquires from the degenerating mass of bacilli the stores of nitrogenous matter they have accumulated, and this affords a very 
good return for the sugars, etc,, which it has previously expended.'* 
