28 
soil free from infection, were taken and 
transplanted, one lot being dippel in a 
solution of lead arsenate, the other being 
untreated. They were then planted out 
in aninfected area. In a little over a 
week all the plants treated with the lead 
arsenate had died off, probobly owing to 
the solution being too concentratel. The 
untreated plants did not show any evi- 
‘dence of attack by the eel-worm. 
Our experiments — show that onions 
transplanted from a sterile seed bed are 
not liable to attack by nematodes, ‘unless 
the bulb be injuredin the process of 
transplanting or by cther agencies. 
— Method of Detectiony the Eggs of 
Nematodes in the Soil, — 
“It is extremely difficult to detect the 
eel-worms or their eggs in the soil, more 
especially is this the ;case in the black 
soils of the Drysdale district. Hundreds 
of micro slides prepared for this soil” 
may be examined without detecting the 
presence of either the nomatodes or their 
eggs. Owin: to the great amount of 
labour entailed by the above method of 
examination, it was necessary to have 
‘recourse to one which would reveal their 
presence in a quick anl satisfactory 
manner. 
The process adopted by Dr. Cobb of 
washing the nematodes out cf the soil, by 
mixing with water, and pouring back and 
forth from one dish to. another, allowing 
the mixture of earth and water to stand 
until the organisms have settled, then 
,pouring off the muddy water, was found 
to be unsuitable when dealing with the 
black soils. 
Our first experiments for the detection 
of the nematodes in the soil was carried 
out somewhat on bacteriological lines. 
Boiled onions were taken and. the pulp 
inoculated with small quantities of the 
affected soil After an interval of twelve 
days, an examination of the pulp showed 
the presence of numerous embryo eel- 
worms, while the uninoculated pulp 
remained The latest method 
adopted by us is on similar lines. A 
quantity of soil:taken ‘from infested land 
is placed ina small glass jar, the soil 
moistened withserile water, and strips 
of onion leaf free from nematodes laid on 
the surface, and examined at intervals of 
sterile, 
THE AUSTRALIAN GARDENER. 
afew days. After a period ranging from 
seven days to a fortnight, the eggs of the 
eel-worm, if present in the soil, will have 
hatched out in the vicinity of the leaf. 
All that is necessary then is to takea 
small fragment of the leaf, place it ina 
watch glass with a little water and exam- 
ine it under the microscope when the 
young worms.can be seen in active move- 
ment, It is even possible to detect them 
by the aid of a good pocket lens. This 
method was found to give positive results 
in all cases when affected soil was sub- 
mitted to examination. 
Samples of soil taken from infested 
land at a depth of 4, 8, 12, and 14 inches, 
were all submitted to the above method 
of examination, and in every case with 
positive results. This shows that deep 
ploughing which turns the soil exactly 
bottom side up, the use of skim _coulter 
to remove the upper layer of the soil, the 
burning of straw or brushwood on the 
surface, and even the use of chemicals will 
have little or no effect on land where the 
soil is liable to crack, thus allowing the 
eggs and embryos to be washed by rain 
storms, or blown by the wind into the 
deeper layers of the soil. 
Of the constituents of the soil, none pro- 
badly are more likely to be moved from 
place to place than minute organisms, such 
as the eggs and larvae, of nematodes by 
the acticn of currents of water on or be- 
neath the surface, It has long been 
known that drainage has an’ important 
bearing on the spread of nematodes, Wind 
animals, in fact anything that moves 
either in or upon the soil, will aot as 
agents in disseminating the disease.— 
(Cobb.). : 
(To be continued ) 
Cultivation of the Potato 
By the Editor of the ‘Queensland Agri-— 
cultural Journal,’ z 
(Continued from last issue.) 
— Potato Scab. — 
This dssease, characterised by the 
presence of scurvy or scab-like patches on 
the skin of the potato, is very prevalent 
during certain seasons ; and, although the 
edible portion of the potato is not in- 
jured, the market value is much depre- 
June, 1910. 
ciated. Theré is also another form of 
scab superficially resembling the one des- 
cribed, caused by an organism called 
Oospora scabies. The disease is prevented 
in both cases by steeping seed potatoes 
for two honrs in half a pint of formalin 
mixed with 15 gallons of water. 
Another remedy is said to be efficacious 
and that is, to dissolve 20z, of corrosive 
sublimate in 16 gallons of water ; when 
fully dissolved, put the seed potatoes in a 
bag and immerse them in the mixture, 
not leaving them to soak, but only long 
enough to ‘ensure that all the seed is 
thoroughly wetted. “Corrosive sublimate 
is highly poisonous, and must be hindled 
carefully, a wooden vessel being used to 
dissolve it in. A potato affection was, in 
1896, brought under the notice of the 
Queensland Department of Agriculture as 
occurring in the Granzow and Alberton 
districts of Beenleigh, and it was found 
to be identical with the new disease of 
the potato plant whose nature and cause 
were first made known in 1894 by Mr. 
Henry Tryon, Government Eutomologist 
The disease was probab y brought into 
the Beenleich district many years since 
in seed potatoes, 
The symptoms of the disease are as 
follows :—. 
When the potato plant is in process of 
vigorous growth,'and’ exhibits every evi- 
dence of health, it suddenly commences 
. to droop as if lacking moisturé; after a 
few hours it generally, becomes flaccid, 
its branches bend downwards, and_ its 
leaves have their edges turned inwards 
80 as to expose their under surfaces. 
These events happen in a few hours, and 
‘the plant thus smitten. never revives, but 
gradually succumbs, On examination, 
the roots and tubers will be found, to all 
appearances, perfectly sound, -; But 
careful examination reveals a faint, ring- 
shaped line, which is seen on the section 
of a healthy tuber at a short distance 
within and parallel to the surface. This 
ring of the healthy tuber-is more evident 
than usual from having become darkened 
in color, Later on,, an opaque. thick, 
white, tenacious fluid exudes in minute 
quantity from the eyes of the tuber, and 
it is this which, causes - the earth to 
strongly adhere to these points when the 
