Aug i, 1900.] 
Supplement to the " Tropical Agriculturist." 
145 
I lately found a clay structure such as wasps 
and similar insscta build, on another tree 
in the same garden shaped and coloured like 
a cocoa pod. Could this be a case of mimicrj-. 
Mr. Weerakoon, Mudnliyar of Wellaboda 
Pattu, Soutliern Province, refers to the tendency 
in the paddyiplant to yield no regular ear of corn, 
the plant I'leing then called Beragas or Borupan 
{Anglice:fahe rush). "I have" he says "seen 
large patches containing snch abnormal growths 
in the Morowak Korale and Wellaboda Pattu, 
sometimes 50% of the plants consisting of the 
" false rush." I attribute the result to inferior 
grain being used for sowing." The writer then 
goes on to ask if it could not be advisable to 
infuse "fresh blood" into paddy by importing 
a good quantity of seed paddy from India. 
-This is what we have advised time without 
number, and we have imported seed from India 
and elsewhere on our own account in a small 
way. It is for Government to take it upon a 
large scale, and the improvement of seed in 
this way should form one of the duties of the 
. reorganised School of Agriculture. 
The same correspondent sends a note on 
"Kadupahara" which he describes as a perenniiil 
plant found growing wild in most places, but 
thriving luxuriantly in the up-country districtSi 
The name is said to be derived from the ground- 
shaped leaves. Tiie leaves, says our correspondent, 
when chopped up and prepared as a dry curry, 
makes a palatable dish, though the Sinhalese 
only use it as a vermifuge for calves. Mr. 
Nock, of Hakgala, is stated to have identified 
it as the "sow thistle," cultivated in some 
countries for the purpose of feeding pigs. Mr. 
Weerakoon recommends it as a desirable addition 
to our list of edible leaves. Dr. Trimen in 
his Flora mentions that Sorchus asper and S. 
oleracens, the common sow thistles of England^ 
are commonly found as weed in cultivated ground. 
ARTIFICIAL CHANGES OF PHYSICAL 
PROPERTIES OF SOIL. 
In this paper the author considers what prac- 
tical means may be employed to impart to culti» 
■vated soils the greatest possible productiveness. 
That the proper cultiTation of the soil is of 
prime importance is shown by the fact that other 
factors important in plant growth, e.y., the plant 
food supplied by manures, can exert their full 
power only when the mechanical condition of the 
soil is favourable. Uncultivated soils generally 
fail to produce maximum yields. The most 
favourable physical conditions exist in those 
soils which consist of a thorough mixture 
of the several principal ingredients. Thus soils 
in which either finely-divided (clayey) or coarsely- 
divided (sandy) ingredients predominate are un- 
favourable to the production of crops without 
decided changes in their properties, wliile soils in 
which the ingredients are mixed in certain pro- 
portions (medium soils) are generally productive, 
it is well known, for instance, that a pure humus 
soil, mainly on account of its physical nature, 
is not favourable to plant growth, but may be 
rendered productive by admixture with a soil 
deficient in humus. 
It is evident that in studying the various ways 
of cultivating soil, not only coiiesion and adhesion, 
but also friction of the soils with the tools and 
the weight of a unit volume of the soil must be 
considered. The force with which the particles 
of soil cling to each other (cohere) is of prime 
importance in connection wir,h cultivation of the 
soil, since the ease or difficulty with which 
tools penetrate the soil, and hence the labour 
required to cultivate the soil, depends primarily 
upon it. The controlling influence of cohesion 
may be inferred from the fact that it is the main 
factor determining the differences between soils, 
although the other properties of soils should also 
be taken into account, since the resistance to be 
overcome in cultivation is always due in part to 
them. In general, it may be said that humus 
offers the least resistance to cultivation, clay the 
greatest, while sand stands between tlie two 
extremes. 
If it be asked what practical means should be 
used to rediuce to a minimum the labour of work- 
ing soils, we should recommend a suitable change 
in composition of the soil as the first step. Thus, 
for example, mixing clay with sand diminishes 
both cohesion and adhesion of the soil, and ren- 
ders it more easy to cultivate. It is true that by 
this treatment both the weight and friction of clay 
are increased, but, as modifications of cohesion 
and adhesion are more far-reaching, the increase 
in weight and friction may be neglected. 
The improvement of the tillable properties of 
soils may be most perfectly attained by an increase 
in the proportion of humus. Tlie working of 
clayey soil is by this means rendered very much 
Jess laborious, because botli cohesion and adhesion, 
and also the weight, are diminished in proportion 
to the amount of humus added. For sandy soils 
also an increase of humus is of advantage, as it 
reduces friction and decreases the weight. It 
thus appears that manuring with materials of 
organic origin (stable manure, vegetable matter, 
straw, and peat) greatly increases the ease of 
cultivation, und at the same time influences most 
favourably the chemical properties of the soil in 
many different ways. Nor should the fact be 
overlooked that increasing the humus content 
promotes the tendency of the soil to assume the 
' crumbly ' structure, and by this means still 
further reduces the mechanical resistance to culti- 
vation. Soils of crumbly structure are not only 
naturally more fertile, but are very much more 
easily worked than those having a separate grain 
structure. Whatever manipulations, therefore, 
promote the formation of the crumbly structure 
and tend to make such structure permanent are 
of great value in soil cultivation, inasmuch as 
they both heighten the fertility of the soil and 
lessen the labour required for its cultivation. 
This is especially true of compact, heavy soils. 
To obtain this crumbly structure and to preserve 
it, several fundamental principles must be ob- 
served. These may be summed up briefly 
follows : (1) The soil must be ploughed imme. 
diately after the crop has been gathered; (2) i^ 
