AuCt 2, 1897.] 
Swpplement to the “ Tropical Agriculturist." 
143 
truth. To till land is to mix the top stratum with 
air. Coarse ploughing of wet lands is leaving the 
great slab-like clods lying loose to dry out their 
water and absorb air instead. Harrowing among 
other ends, mixes air very complcely with the 
loose tilth. But the most thorough and effective 
addition of this necessary i.igredient is obtained 
by the process of trenchiruj By trenching almost 
every cubic inch of soil is disassociated, large 
cavities full of air are left open among the loosely 
thrown up earth, and although these diminish a 
good deal by pressure of tlie superabundant mate- 
rial, yet the air they contain forces its way into 
the microscopic interstices between particles far 
smaller than grains of sand. 
So much for the air supply demanded by the 
root respiration. Let us consider the water supply. 
It is unfortunately the current belief that trees 
must have water given to them much in the same 
way as one waters a house. Either whole 
bucketsful are poured in at the base of the trunk, 
or (in irrigating) a stream is turned on to flood its 
surroundings. This is in direct opposition to the 
way in which trees take up their water supply. 
“ It is characteristic of the mode of life of land- 
plants,” says Sachs, “ that they only flourish as 
a rule, when their roots are evenly distributed 
throughout a soil that is relatively dry, only 
partially flooded with water.” The practice of 
agriculture bears testimony to this fact that damp 
lowlying lands are made highly fertile by an ade- 
quate drainage which renders them relatively dry. 
The culture of plants in green-houses teaches that 
land plants rooted in pots very easily perish if 
they are watered too often, and one of the first 
lessons a garden apprentice receives is “ to keep his 
watering can quiet.” Land plants, and particularly 
trees, carry on their root-functions continuously 
only when the soil surrounding them is relatively 
poor in water. A complete saturation must be 
very briet and soon relieved by draining away, or 
else it acts injuriously. Let us consider how the 
enormous losses of water by daily transpiration 
from the leaves are made good by inhibition from 
soil, not wet but only just perceptibly moi.st to 
the touch, and therefore in the best po.ssible con- 
dition for sustaining healthy root-growth. Every 
minute particle of earth, even down to those too 
small for distinct vision, is enveloped in a thin 
film of adherent water held fast by surface attrac- 
tion, almost as if it had been dipped in water and 
brought out wet. Where particles by reason of their 
angular shape happen to get closely together, he 
attractions combine to hold a thicker watery 
layer. The remaining interstices are filled with 
air. Among these surface-wetted particles the 
root hairs make their way, clinging tightly to 
them with their porous cell-wall and absorbing 
such part of the watery layer as they touch. It 
needs little knowledge of the laws of diffusion and 
capillary attraction to see that the fluid so absorbed 
is made good by neighbouring water-particles, and 
that, given absoiption at any iroint, an indraw 
takes place towards it. Every root-hair then is a 
centre of attraction to the water constituting the 
moisture-layer of all particles of earth within its 
range. And such absorptions, multiplied by 
millions, amply supply the almost incredible num- 
ber of gallons ,of water daily transpired as vapour 
from the foliage of a large tree. 
But have these physiological facts any value 
in practical work ? Much every way, as we 
shall see. 
(To be continued.) 
♦ 
THE KECENU HORSE PLAGUE 
AT MANNAR. 
All epizootic among horses and donkeys broke 
out at Mannar about the latter part of March. 
Only a comparatively few donkeys succumbed to 
the disease ; but the number of ponies attacked up 
to the 4th May was about fifty, and of these 
none recovered, A similar outbreak is reported to 
have taken place some twelve years ago. 
It is needless to say tiiat a veterinary surgeon 
would have been the fitte.^t person to investigate 
the nature and cause of the disease, and it is rather 
unfortunate that such an officer could not have 
been present on the spot during the out- 
break. In the absence, however, of any informa- 
tion from a veterinarian, we have to rely on the 
reports of the Adigar and the District Medical 
Officer of the place. The report of the latter es- 
pecially is very welcome, under the circumstances. 
The most striking symptoms, as given by the 
Adigar, are that the animals begin to lose flesh, 
and in the course of 20 or 25 days they are reduced 
to mere skin and bone, fall to the ground and 
die. 
The Medical Officer goes more into details and 
describes the symptoms as follows : — “ Loss of 
appetite, great thirst, dyspnoea, constipation, rest- 
leesness, inability to walk, and when attempting 
to walk the horse falls down. While in the recum- 
bent position, he shows restless movements of the 
limbs and body. In some cases there was no 
passing of dung at all, and in others the dung 
passed was dry and scanty Most of the horses 
were lound dead by the side of waterp mN or 
ponds. Ea.st breathing was a very notice. .ble 
symptom.” 
This description of the symptoms would have 
been more complete had we been told whether the 
re.«piration was tlioracic or abdominal, and if a 
record had been kept of the temperature and pulse 
as well as of the number of respirations, per minute, 
at stated intervals during the progress of the 
disease. Auscultation and percussion should have 
been helpful to the diagnosis. The nature and 
quantity of the urine ought to have been noticed, 
and the condition of the skin and mucous mem- 
brane also observed. 
The postmortem examination held by the 
Medical Officer however gives some valuable infor- 
mation. He examined three carcases and found the 
lungs inflamed in all of them. In the first case, 
except I of the lungs the rest was all inflamed, 
and this horse died in the first stage of pneumonia. 
Tlie second horse examined died in the second stage 
of pneumonia. The other one died in the first stage. 
As the re.sultof his examination, the Medical Officer 
feels certain that the horses died of an epizootic 
form of pneumonia. It would have been useful 
if the pleunc v. c i also specially examined in order 
to find wlielherthey were involved in the inflam- 
matory condition. 
The Adigar thinks that the disease was caused 
by feeding on bad pasture. During the heavy 
