496 
THE 
GARDENERS’ 
CHRONICLE. 
[Apri 20, 1895, 
PLANT DISEASES. 
Tue following is the text of an important lec- 
oke, on air diseases, 
at the conversazione of the Horticultural Club on the 
9th inst. The iwportance of devoting more search- 
ing an 
ut, unfortunately 
do 
viimsi effort, 
Department, which gene to a D 
Agriculture, but the very meagre 
additional evidence of the indifference which charac- 
terises the “ higher powers, in all which concerns 
the diseases of plants. How disastrous these diseases 
may be has been exemplified by the damage done to 
corn crops in Australia, Apple crops in parts of the 
United States, to Coffee in 
or Opium Poppy in India, the 
acco crops in Australia, 
was not until the diseases became 
There is no reason t that it is possible to 
methods of remedy which have been applied in 
simil s when any one these err. 
m disaster, and a large industry is thre 
with ruin—and not until then, do we hear = act 
for scientific investigation, and suggestions of 
remedies, 
Tue Causes or DISEASES, 
cally conversant with horti- 
Those w 
* will be ready to dae that diseases in p 
have several cause hey m es ae from the 
yb 
ted as euch, in which no trace of fungi could be 
fei, and the 1 e could only be 
attributed to bad cultivat 
It is not our een, et occupy = time with 
allusion to any other of the diseases of plants th 
those produced by the attacks of fungi; but 
making those observations to which we desire chiefly 
direct your attention, we might offer 3 
upon a closely- related subject. W. will pa 
seases animals, 
adds eee owed, which leads to 
the eee that are not only present, 
but are the primary cause cae many forms of animal 
ase. In past times we Sern of zoo 
botany in terms which led to the inference that life 
being the case, and there are more 
Poe than we commonly admit, then there may 
between the diseases of animals 
and of 
and those of plants. This was pointed out, o 
memorable occasion, by Sir James et and 0 
enunciated. 
nian Vine disease, that pre 
plants by inoculation with 
Cucumbers, Admitting all this to ba substantiated, we 
are face to face with a new aspect of plant disease 
corresponding i npea scarlatina, typhoid, and 
other zymotic diseases of animals, and a question to 
which horticulturists would 2 well to keep open ears 
and obse t 
In the case of diseases in the human subject, we 
know how much depends upon an accurate diagnosis 
of the disease; the symptoms must be studied and 
compared, and when the true nature of the disease 
been ascertained, the proper remedies can be 
N but it is useless to think of remedies 30 long 
s the true nature 1 the disease has not been ascer- 
Abel, ecisely the same course has to be adopte 
with plants en from disease, and it is our first 
duty to avail ourselves of every facility . deter- 
mining the nature of the disease. Even if we sup- 
pose that any and every man who is NDE in the 
cultivation of plants has the primary knowledge 
whic 
o 
y insects or by 
ques 
fungi, or whether it gti from some error in cul- 
tivation, this would be a step that the 
majority would take ied te diagnosis, 
iagn 
We more would be e may apt gathered from 
me further remarks with which we will venture to 
rode e you, 
EnpopHytat Funcorp Diseases, 
Diseases of fangoid origin may be classed i in two 
which we may 
in—outwards, analogous to small-pox; 
the N commence externally, and establish them- 
selves on the surface 
as bunt and mildew in corn crops, with such 
diseases of ornamental plants as the Hollyhock 
disease, and the brand which affects the foliage of 
Sweet ‘Wiliams and others of De Pink family. 
There are some festures in common, but there are 
other considerable esns in ya life-history 
and reproduction i wo types of moulds and 
ee 
Aro 88 2 8 the importance which 
; knowledge fe-history should hold in 
the estimation cultivator, v 
y to some 0 
in By numbers on ref fertile _ thread 
a pee outer coating of membrane, with fluid — 
These contents soon becom 
e 
smaller ee which have been dif- 
aga in its interior escape, each one furnished 
ity with a a pair of delicate moveable 
— by means of which these little bodies, now 
termed-zo0spores, can swim actively in any thin film 
— 
of moisture upon which they may fall. Possibly 
this film may be on the leaf of a foster-plant. Ina 
short time all motion ceases an 
the th 
singly, sometimes in tufts 
conidium at the tip e 
ans of w assed from leaf to leaf, 441 
7855 plant to 7 until the whole area is affected. 
How many of the minute conidia may be transported 
to a considerable distance by a breath he: wind it is 
impossible to say, but it is known that they are 
. — of suspension in the air, and be: they may 
be carried to any spot where there is sufficient 
me for the conidia to be differentiated in 
zoospores, and afterwards come 8 rest and germi- 
his process takes place in summer and 
autumn; but there is yet iia means by which 
the pest is disseminated in the spring. 
The mycelium which flourishes within the sub- 
stance of the plant infested is capable of producing 
peek A globose bodies, chiefly within the stems, con- 
from external view. hese globose bodies 
peas a thick e mostly of b colour, 
ola. stems of plants 
mould during the autumn conceal within themselves 
during the winter a large number of these “ resting 
spores.” As the old stems rot aad decay resting 
i peri 
w 
2 
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oe 
f 
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D 
e 
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c 
— 
E 
æ 
EA 
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m 
T 
— 
— 
i=] 
S 
2 
5 
. 
5 
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2 
of activity commen 
globose Huge become “differentiated into a consider- 
able n umber of zoospores, Were ultimately escape 
b rupture = the thick envelope, armed with 
vibratile cilia, and in all — like ‘the mange 
for an attack upon seedlings in the spring. 
be inferred that in order to check the spread of these 
out est 
on resting spores, revent bi 
infection of seedlings in the iiai "Thus it will 
seen that a knowledge of the life-history of these 
methods to be 
parasites will suggest . best 
employed in their destru 
Time forbids —— — of the 
lee of th and smut fu 
8 
Ss 
diseases greatly 
cereal grasses, —— N ref them ‘attack oe 
plants, 
at 
