Sept. 1, 1894.] Supplement to the "Tropical Agriculturist." 
211 
We are told that the Engineers iti charge of 
the Mexican central railway reported that in the 
building of the road, it was noted that with 
the coming of the construction train, bearing 
great quantities of steel rails, that the rain fell 
in advance of the train at unusual times and 
in unusual quantities. It is therefore inferred 
that in the construction of railways the elec- 
trical conditions of the country are disturbed 
that have an influence upon precipitation. The 
cultivation of the soil allows of moisture which 
falls to be absorbed by the soil, rather than 
allowing it to run off as is the case in hard ami 
unworked soils, hence a greater amount of 
moisture is present in the soil, which evaporating, | 
produces a higher percentage of moisture in the 
air; the food for a storm is heat and moisture, 
hence the influence of the cultivation of the 
soil is faciliating the deposit of moisture. The 
planting of trees serves a two-fold purpose in 
this connection. The leaf surface of the tree 
is very great, when the aggregate is considered, 
hence can be seen the great amount of increased 
humidity obtained from the moisture which is 
thrown off by the leaves ; secondly, the root s 
of trees serve as a sponge, when taken in con- 
nection with the soil. Surrounding the roots, 
which serve to absorb and retain moisture and to 
allow its gradual escape to spores, thus affording a 
more constant supply to the streams, preventing 
t/heif drying up and aff mling a greater amount 
of moisture to the atmosphere. The various 
systems of irrigition, distributing moisture to 
the soil which in turn is absorbel by the vege- 
tation and finally evaporated, furnishes a most 
satisfactory means of unking the air more humid 
and of miking the conditions mire favourable 
for possible rainfall. All of these conditions 
combined add very greatly to the moisture of 
the air, hence food for the stonn and facilitate 
the possibility of rain, when without these artificial 
means rain would be practically impossible. 
Hence it may be considered that the opening 
up of the laud to tillage, planting of trees, 
the building of railroads and general covering 
of many square miles with vegetation that were 
formerly barren wastes, have a tendency to re- 
tain the moisture from the clouds, and this in 
turn renders the air more humid, so that there 
is an actual increase in She moisture of the air, 
beneficial to vegetation* 
THE AMERICAN DHWBERRY. 
Some months ago we received a small parcel of j 
the dewberry from the Saharanpur Gardens. | 
Some of these seeds we distributed for trial in ! 
high as well as medium elevations, but have not I 
heurd witli what result they were planted. We 
are, however, pleased to note that Mr. J, W. Ebert, 
Superintendent of the Dematagoda slaughter- 
house, has succeeded in raising a healthy plant, 
his other seedlings, as lie believes, having been 
originally weeded out by his coolies. It will be 
interesting to watch the progress of this single 
plant, growing, as it does, in an apparently un- 
congenial situation as regards elevation and 
temperature. In the Mayflower for June 1893, 
appears an excellent coloured plate of the dew- 
berry, and a description of the plant, from which 
we cull the following : — Among the most delicious 
berries of recent introduction are the dewberries, 
which are running or climbing varieties of the 
blackberry. They may be allowed to trail upon 
the ground, be trained on a trellis, or tied to a 
stake like a grape vine. When in flower, the 
tree is usually covered with manes of large, pure 
white, sweet-scented flowers, which are succeeded 
by a profusion of delicious fruits which are larger, 
richer, and more juicy than blackberries. The 
fruit ripens about two weeks earlier than most 
varieties of blackberries. It makes a delightful 
wine for invalids, possessing the same delicious 
flavour as the berries. The vines are perfectly 
hard, and do not sucker from the roots, but 
increase from the tips. 
«. 
SOIL INOCULATION. 
Nobbe and Hiltner have during the last few 
years carried out some important researches in 
this subject at Tharaudt. The power which 
different leguminous plants possess of fixing free 
nitrogen by means of their root-tubercles varies 
widely in different cases, and is largely dependent 
on the nature of the soil. The bacteria in the 
tubercles of different genera all seem to belong to 
the same species (Bacterium radicicola), but are so 
energetically influenced by the plant in the roots 
of which they live that they lose more or less the 
power of infecting other leguminous plants, except 
those closely related to the kind which they 
inhabit. The practical outcome of this is that 
when any special leguminous plant is sown in a 
particular kind of soil, it will only develop 
tubercles on its roots if (a) unmodified root 
bacteria are present, or (6) root bacteria modified 
by living within closely-allied species. («) will 
be the case if no leguminous plants have bee n 
grown on the land in question, or if they have 
not been grown for a long time ; (l>) will happen 
if the same or a very similar crop has recently 
grown on the land. If, however, the last crop 
been a ltgumiuous one of very different kind, the 
new crop will either develop no tubercles or the 
tubercles will be few and small, this being associ- 
ated with little or no power of fixing free nitrogen. 
This will be the case, for example, if clover 
follows peas. The farmer, therefore, in cultivat- 
ing leguminous crops must take care that the 
soil is properly inoculated with earth from a field 
which has grown the special crop the previous 
year. The inoculating earth for peas must be 
taken from pea-fields, clover from clover fields, &c. 
In an experiment made in peas by Dr. Salfeld, 
soil from a pea-field distributed at the rate of 
17 cwt. per acre, produced a marked effect. 
This soil is taken from the part where the roots 
are situated, strewn on the read}- prepared field, 
and harrowed in. To what extent the bacteria 
from one kind of leguminous plant will infect 
other kinds needs careful determination ; but this 
much is known that pea bacteria will infect 
vetches and vetch bacteria peas, while on 
the other hand pea (and vetch) bacteria have no 
effect on clover, and vice vena. The fact that 
the root bacteria undergo modification in different 
plants has not been sufficiently taken into con- 
sideration in past researches, and this accounts 
or some of the discrepancies between the obser- 
