Sept. 1, 1898.] Supplement to the " Tropical Agriculturist." 
227 
INOCULATION OF PLANTS AGAINST DISEASE. 
The June number of the Queensland Agricul- 
tural Journal contains an interesting contribution 
from the pen of Mr. Henry Tryou, the Entomo- 
logist, on Preventive Treatment in Plant Diseases. 
The writer first refers to Hybridisation as a means 
of warding off plant diseases, and cites as 
examples of the successful employment of this 
method, the production of a rust-resisting wheat 
and phylloxera-proof vines. Success has even 
been attained in preventing "chlorosis" and 
" mildew" in grapes, and a kind of leaf disease in 
the strawberry by hybridisation, and Dr. Vou 
Tubeuf, the eminent German authority on Plant 
Pathology, has stated that he considers the method 
as available in preventing many diseases in 
cultivated plants generally. Mr. Tryon considers 
that it might be possible to keep off the woolly 
aphis or American blight from apple*, the fruit 
maggot fly from plums, and "black spot" from 
pears and apples by the same means. 
As regards inoculation against plant diseases, we 
shall quote Mr. Tryon's remarks in extenso; — 
With regard to this j)rocedure little beyond 
general considerations can be adduced in support 
of its employment as a means for preventing the 
occurrence of disease in plants. 
Many maladies that they exhibit present this 
feature — viz., their active agents, whether germs 
or other bodies, are restricted i;i the first instance 
to the vessels or to the tissues with which these 
are immediately in connection. As instances of 
this may be mentioned the gumming disease of 
sugar cane caused by a microbe, Bacillus vascu- 
lorum, Cobb, in the vessels thereof ; and the new 
and most destructive disease of the potato, dis- 
covered by the writer and found to be occasioned 
by the presence of Bacillus vasculonan-solani, Tryon, 
similarly related to it ; and the same obtains in 
other diseases with regard to the tissues. 
Again, it is possible to introduce small dosages of 
chemicals or other reagents into the vessels and 
tissues of plants without prejudically affecting the 
vigour and health of the latter. As an instance of 
this may be mentioned the Hydrangea, the flo.vers 
of which are pink or blue, in correspondence with 
the plentiful or comparatively pauce occurrence 
of a-vailable iron in the soil in which it is grown. 
Moreover, it has been found that when vines have 
been sprayed with Bordeaux mixture their leaves 
absorb into their tissues an appreciable amount of 
copper from the copper sulphate that this fungi- 
cide contains. Again, a permeability of plant 
vessels and tissues to bodies of various kinds, as 
well as the general translation of these when once 
introduced, is shown by well-known physiological 
experiments. 
Chemicals or other reagents may therefore be 
brought into contact with the germs or other 
bodies originating disease, and either destroy 
tliem or counteract or inhibit their action. Thus 
an Italian investigator, Pichi, has alleged that 
expeiimental evidence is forthcoming to prove 
that the absorption by the foliage of the vine of 
copper sulphate is preventive of the occurrence of 
mildew occasioned by the growth of the parasitic 
fungus, Peronoxpora viticola, in the tissue- A. N. 
Berlese, however, iu commenting on this finding by 
P- Pichi, alleges that iu using a solution of copper 
sulphate as weak as that mentioned by the latter 
there would be no deposit of copper sulphate in 
the tissue, and therefore no such action manifest- 
ed as that implied. It may, however, be pointed 
out that this objection would appear to lack 
soundness, for, as has been subsequently demon- 
strated by Dr. Meade Bolton, pieces of metal that 
are absolutely pure, and not only such as are 
commercial and marked chemically pure, will, 
when placed in pure cultivations of different 
micro-organisms, notwithstanding they are practi- 
cally insoluble in the media of these cultivations, 
inhibit or prevent the growth of these organisms 
in a very marked manner; and in the absence of 
any suggested explanation of this phenomenon it 
may be presumed that a germicidal action by 
infinitesimal quantities is being displayed. 
The introduction of metallic salts into the tissue 
of plants, moreover, forms the .special feature in 
a treatment employed in France, with — iu some 
instances — marked success, in obviating the pre- 
viously mentioned vine disease chlorosis, and 
known as " Badigeonnage Rassiguier." This treat- 
ment consists in applying to all the fresh surfaces 
exposed by the pruning scissors or " secateur " 
a strong solution of sulphate of iron, at a time 
when there is free movement of the sap (i.e., in 
October, in France). The absorption (states Eassi- 
guier) in this case takes place rapidly ; and, after 
some days have elapsed oa cutting a "courson" 
or a " bras de souche," it is easy to detect traces 
of sulphate of iron by following up the tissue of 
the plant, In fact, according to L, Degrully, this 
solution can be observed to penetrate into the 
body of the branch from 10-12 centimetres below 
the point of insertion of the shoot through which 
the solution has entered. The benefit following 
the adoption of this process of inoculation has 
been fully deslt with by the last-mentioned 
Authority, and would appear to be very pro- 
nounced. 
From the foregoing statements it would seem 
likely also that there may, after all, be some 
grounds for concluding that the observed freedom 
from disease, said in some instances to follow the 
act of driving metallic nails into the wood of fruit 
trees, may stand in the relation of cause and 
effect. 
With regard to other forms of inoculation for 
preventing disease in plants it may be remarked 
that, though those maladies that might be attri- 
butable to the presence and action of bacteria 
have been little studied, " there are (to quote Dr. 
Erwiu F. Smith) in all probability as many 
bacterial diseases of plants as cf animals," More- 
over, with regard to the bacteria that pro(.ucaJ 
maladies in pLints, it may be further affiimt-d (iiat 
they are clo>ely rt-lated, both binlovicjilly iind 
morphologically, to bacteria that produce maladies 
in animals. Again, in the course of their growth 
they both may produce acids, alikalies, enzymes, 
or other bodies. Thus, whereas in the ca-o of 
animals immunity may be secured by inoculating 
into their systems products derived in the course 
of their development from pathogenetic bacteria, 
so also the same may happen when similar inocula- 
tion is peiformed on plants, and this seems 
especially probable since it has been demonstrated 
that tlie di>ease itself, with its casual agents, can 
be communicated to them by this procedure- 
