‘ 
514 ; QUEENSLAND AGRICULTURAL JOURNAL. [1 Juve, 1898. 
presenting the excellencies that the latter already possess, have also the special 
resisting quality to the attacks of the fruit-maggot fly so conspicuous in the 
former. ; 
Similarly, advantage might be taken of the different extents to which pears 
and apples are affected by Fusicladium, or “black spot’’ disease, to raise 
excellent fruits of these kinds free from the presence of this malady. 
However, as in the case of the so-called “ making’ of rust-resistant 
wheats, hybridisation must be entered upon with the exercise of judgment and 
followed by discriminate selection ; otherwise results other than those sought 
will be attained. As an instance of this may be cited the following :—‘ We 
have (states a writer) had under observation an interesting hybrid between 
De Soto Plum (Prunus americana) and an Oregon Plum (Prunus domestica 7). 
In habit of tree and foliage the hybrids assume the characters of Prunus 
‘americana, our Wild Plum. ‘This variety is [however, found to be] strongly 
prepotent in transmitting not only its special characteristics, but also a 
tendency to take a disease (Cladosporium carpophilum), which does not occur 
in our cultivated European Plum (P. domestica).”* 
INOCULATION, 
With regard to this procedure 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 in 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 amicrobe, Bacillus vasculorum, Cobb, in the vessels thereof ; and the 
new and most destructive disease of the potato, discovered by the writer and 
found to be occasioned by the presence of Bacillus vasculorwm-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 prejudicially affecting 
the vigour and health of the latter. As an instance of this may be mentioned 
the Hydrangea, the flowers of which are pink or blue, in correspondence with 
the plentiful or comparatively pauce cccurrence of available 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 fungicide 
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 them or counteract or 
inhibit their action. Thus an Italian investigator, Pichi, has alleged that experi- 
mental 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, Peronospora viticola, in the tissue.t A. N. 
Berlese, however, in commenting on this finding by P. Pichi, alleges that in 
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 manifested as that implied. It may, however, be pointed out that 
this objection would appear to lack soundness, for, as has been subsequently 
demonstrated by Dr. Meade Bolton, pieces of metal that are absolutely pure, 
and not only such as are commercial and marked chemically pure, will, when 
* “©Oross Breeds and Heridity.”—“ Rural Life,” 19th Oct., 1898, p. 12 (quoted in Bull. 23 
Towa Agr. Exp. Stat. 1893. Op. cit., p. 915). 
+P. Pichi: ‘‘ Alcuni esperimenti fisiopatologici sulle vite in relazione al parassitismo della 
Peronospora.” Bull. Soc. Bot. Ital.—1891, No. 2; 1892, No. 5, Abstracted at length by A, N. 
Berlese in ‘‘ Rivista di Patalogia Veget.” I., pp. 325-7, 1892. . : 
