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1903] BRIEFER ARTICLES 65 
The prevailing opinions held have been that leguminous root 
tubercles are destroyed at the close of the seasonal vegetative period 
and that the cytoplasmic and albuminoid contents of rhizobia are 
absorbed or assimilated by the host plant. Upon examining the roots 
of Trifolium pratense \ate in November it was found that the tubercles 
present were normal in appearance. Microscopic examination showed 
that rhizobia (2. mufadile) were present in smaller numbers than during 
the summer months. The highly refractive sporoids (fatty particles) 
were more plentifully present and more distinct. Since the tubercles 
were intact the question arises, what became of the missing rhizobia? 
It is highly probable that through lack of nutriment they became 
famished and finally died. Most organisms present reacted very 
feebly with the usual cytoplasmic stains, indicating a reduction in the 
cytoplasm. In such rhizobia the above mentioned sporoids were very 
distinctly visible and took the stain readily. Each organism showed 
from one to five such sporoids, more usually one in the neck portion 
and two or sometimes three or four in the body of the Indian club- 
shaped rhizobia, and quite generally occupying a position next to the 
cell-wall. They are not uniform in size and form. They stain a 
reddish brown with iodin tincture and are very clearly shown in an 
aqueous solution of corrosive sublimate. Infecting threads (Infections- 
faden) are present in apical areas and show no special modifications. 
In some tubercles they seemed to be wholly wanting. When present 
they are usually very distinct for several reasons, because of the lesser 
abundance of rhizobia and also because of the greater thickness of 
the cellulose wall. They are almost entirely empty, containing only a 
few small motile forms of the rhizobia. The walls of the filaments 
attain their maximum thickness late in the fall of the first season; the 
following season they do not increase in thickness, though they become 
refilled with motile rhizobia, finally rupturing the wall or escaping 
through breaks already existing. Thus they again refill the cells with 
mature, greatly modified, non-motile rhizobia. During the second 
year’s growth of the tubercles, the filaments often disappear entirely. 
They may be destroyed or assimilated by the rhizobia or by the host 
plant. In some instances the filaments become separated from the 
cell-walls because of the tension due to the growing cell. ‘The separa- 
tion may take place in any part of the threads, but more commonly 
where they unite with the cell-wall. During the second season the 
Partially emptied infected area of tubercles again becomes tensely 
filled with mature rhizobia, through the multiplication of organisms 
