36 REPORT OF DEPARTMENT OF BACTERIOLOGY OF THE 
Alfalfa nodules occur singly and in clusters of various kinds. 
They are usually found upon the fine roots or attached to the larger 
roots by a short branch. The single nodules are usually about the 
size and shape of an alfalfa seed but in exceptional cases they may 
be larger than a kernel of wheat. Often two or more nodules are 
attached at a common point and radiate like a fan. At times an ir- 
regularly shaped mass is formed from which the nodules radiate, 
resembling the palm and fingers of the hand. In some fields there 
is an abundant formation of giant clusters, often a half-inch across, 
in which large numbers of the individual nodules are set together in 
a mass radiating from a common center, at which they are attached 
to a fine root. 
The prevailing color of the young growing nodule is white, often 
with a tinge of green at one end. The older nodules are darker in 
color, possibly through staining by the soil solution. Late in the 
season many of the nodules appear brown and shriveled as though 
their contents had been withdrawn. 
flow to tind the nodules—— When conditions are favorable nodules 
are formed very promptly. In some germination experiments by 
F. C. Stewart, Botanist of this Station, nodules were well devel- 
oped by the time the first true leaves were formed and the seedlings 
were less than an inch high. A photograph of slightly older seed- 
lings is shown in Plate II. 
The nodules are most easily found during the first two seasons 
since the root systems are then comparatively near the surface. 
With each succeeding season the fine roots are at greater depths 
and the difficulty in finding nodules is proportionately increased. 
~The nature and condition of the soil are also considerable factors 
in the chance of success, In clay ground, particularly when it is 
dry, it is difficult to remove the dirt from the roots without remov- 
ing the nodules at the same time. In light, sandy soils, especially 
when these are moist, there is little chance of overlooking the 
nodules if moderate care is exercised and the person knows a 
nodule when he sees it. 
It is best to dig up a block of earth containing the plant to be 
examined and if the soil is in the proper condition the dirt may 
be carefully removed from the roots with the hands. If the soil - 
is hard and dry it is best to use water in separating the dirt from 
the roots. Where plants are pulled up bodily as is sometimes done 
the nodules uniformly remain in the ground. The number of 
nodules will often vary greatly on adjoining plants and a consider- 
