1899 
THE RURAL NEW-YORKER. 
35 
TUBERCLES ON PLANT ROOTS. 
THE WONDERFUL WORK THEY DO. 
A Great Field for Study. 
Of Different Shape. —I have lately 
been examining with considerable inter¬ 
est the nodules on roots of clover, peas, 
beans, etc. I infer from what I have 
read that nodules on different plants 
are produced by different varieties of 
organisms. I find that the nodules on 
the several varieties of plants vary in 
size and shape. Those on clover, both 
Red and Crimson, are small, elongated 
egg shape, and are not as numerous or 
as large as these on Canada peas. I did 
not find any on clover more than about 
1-16-inch in length, and less than half 
that in diameter. On peas, they were 
nearly twice as long as thick, and some¬ 
what different in shape. The base joins 
to the pea root, and extends outward 
about the shape and size of half a grain 
of rye cut crosswise. Sometimes sev¬ 
eral grow into a cluster joining to each 
other, so that they present much the 
shape or form of branching coral. In 
some instances, as many as six or eight 
are thus joined. I think they always 
grow to full size singly, and others grow 
from them after. 
Peas growing in my peach orchard 
have the roots very thickly supplied 
with the nodules, dozens or scores on a 
single plant. Peas have been grown on 
the land several years in succession. In 
1897, I plowed up my old strawberry bed 
after harvesting the crop, and sowed it 
to oats and peas. They made only a 
feeble growth. Last season my straw¬ 
berry field adjoined the old one, and I 
plowed it up and sowed peas and corn. 
The peas made a growth of 12 to 15 
inches, and then nearly all died, except 
a few around the border. On the border 
adjoining the previous strawberry field, 
where peas were sown last year, the pea 
roots are fairly well supplied with nod¬ 
ules ; but on the opposite side of the 
field, very few nodules could be found 
on any of the pea roots, most plantshav¬ 
ing none. I could find none on the dead 
plants anywhere, but they may have 
decayed. 
Where Do They Originate ?—I 
sowed some cow peas which made quite 
a good growth. There were some nodules 
on the roots, but not numerous. They 
were very large, however, irregular 
angular bodies, some as much as %-inch 
in diameter. No cow peas have ever 
been grown in this vicinity before, and 
the seed used was so old that the owner 
dared not sell it for seed ; it came up 
well, however. The question is sug¬ 
gested, Where did the germs which pro¬ 
duced the nodules come from ? Do they 
exist on the roots of some other plants 
which have grown here, or did they 
come with the seed sown ? If the latter, 
then their vitality is not destroyed by 
as much as three years’ exposure to dry 
air. If the power to gather nitrogen is 
in proportion to the supply of nodules 
on roots, I should think Canada peas the 
best crop to sow for enriching land, as 
in cases I have observed, they are much 
better supplied with nodules. 
I find the nodules on common garden 
beans, small, irregular, rounded bodies, 
the largest near J^-inch in longest diam¬ 
eter, and on some plants, I find them 
quite numerous. I notice one similar 
habit of growth of nodules on all the 
different plants which I have examined— 
I found them only on roots which run 
near the surface, the deeper roots of 
beans and clover showing no trace of 
them. m. m. 
Medway, Mass. 
Comments by Dr. B. D. Hoisted. 
Most Galls in Poor Soils. —The 
whole subject of root tubercles is a com¬ 
paratively new one, and there is much 
to be found out about it. It, however, 
seems settled that a close relationship 
exists between the taking up of the free 
nitrogen by plants and the presence of 
galls upon their roots. The majority of 
plants do not have such root tubercles, 
TWO PEA ROOTS SHOWING ROOT TUBERCLES. Fig. 15. 
ROOT OF WAX BEAN SHOWING TUBERCLES. Fig, 16. 
as, for example, the cereals, potatoes 
and the like, while clovers, and clover¬ 
like plants, are generally gall-bearing, 
when the circumstances are favorable 
for their formation. When a soil is rich 
in combined nitrogen, the tubercles are 
much less liable to form than when the 
soil is poor in such substances. The 
host plant needs to be “hungry” for 
nitrogen for the full development of the 
tubercles. These galls are produced by 
microorganisms closely related to the 
bacteria; they make their entrance from 
the soil through the tender cell walls of 
the younger portions of the roots, and 
induce a cell growth in the region of the 
invasion that results in a tubercle. 
In some unknown way, the tubercle 
germs are able to lay hold and adapt the 
free nitrogen for the use of the plant 
that is bearing the galls. To a certain 
extent, the number and size of the galls 
may be taken as an index of the success 
of the plant. It is difficult to satisfy M. 
M.’s mind upon the point of the best 
crop to grow for renovating the land. 
There are so many sides to such a ques¬ 
tion that one would need to know the full 
history of the case to offer any advice. 
The Germs Are Alike. —There is a 
marked difference between the galls 
upon the roots of leguminous plants ; 
for example, those of the pea are quite 
unlike those of the bean. This is 
brought out in Figs. 15 and 16, made 
from sun prints of the roots and their 
galls. Those of the beans are nearly 
spherical, and usually most abundant 
near the base of the stem, and but few 
are met upon the ultimate ramifications 
of the roots. The pea galls are irregular 
and somewhat fan-shaped in outline, 
and generally distributed along the 
main or tap root. From the great differ¬ 
ence in size, shape and distribution, one 
might easily think that they were 
caused by distinct kinds of germs; but 
there is no marked distinction in the 
microorganisms when studied with the 
microscope. It is true that a germ that 
has grown upon a certain crop plant is 
more at home upon that kind of host. 
In other words, soil-extract from an old 
pea field will produce galls upon pea 
roots in new land better than upon clover 
or any other crop. 
This leads to a word upon the subject 
of soil inoculation. The study of the 
tubercle germs has gone so far that now 
they are isolated and sold in the market 
under the trade name of “ Nitragin”. 
This is a “starter” in land when the 
germs are not present; very good results 
have come from the use of this germ fer¬ 
tilizer. A small bottle of it is enough 
to make a difference of tons of yield in 
certain crops, as shown by experiment 
at the Alabama Station with Crimson 
clover and Hairy vetch. Of course, soil 
that contains the germs may be used in 
the same way, and in some instances, a 
ton or less of old soil where a clover or 
clover-like crop has been grown, may be 
spread upon land new to the same crop 
there to be grown, with excellent re¬ 
sults. During the past year, in one ex¬ 
periment at the “Plant Hospital”, I 
found that soil from old pea land made 
a striking difference upon new soil, in 
the larger growth and deeper green 
color of the pea plants. The yield of 
pods was also increased. There is a 
large field for study in these tubercles 
and the service they render the foster 
plant in the securing of a supply of 
nitrogen. byron d. halsted. 
New Jersey Experiment Station. 
R. N.-Y.—In the June, 1898, issue of 
the Industrialist, issued at the Kansas 
Agricultural College, D. H. Otis gives an 
account of some inoculation experi¬ 
ments. Soil in which Soy beans had 
grown in Massachusetts, was brought to 
Kansas, and used to grow Soy beans 
there when mixed with Kansas soil. 
The tubercles were formed in this mixt¬ 
ure, and this Kansas soil was afterward 
used to inoculate other soils. Mr. Otis 
says that this inoculation is entirely 
practicable. 
