a 
1 Juve, 1898. ] QUEENSLAND AGRICULTURAL JOURNAL. 511 
Vegetable Pathology. 
PREVENTIVE TREATMENT IN PLANT DISHASE. 
HYBRIDISATION AND INOCULATION. 
By HENRY TRYON, 
Entomologist 
Ty an address delivered on 28rd April, 1898, before the Wellington Point 
Agricultural, Horticultural, and Industrial Association on “ Preventive Treat- 
ment in Plant Disease,’ including in this category changes consequent on 
insect injury, the writer maintained that the hybridisation, cross-fertilisation, 
and inoculation of plants were procedures by the adoption of which plant 
maladies might be obviated. ; 
__ By those not already conversant with the results already obtained in these 
provinces of special research, this proposition might be received with reasonable 
scepticism ; and such an attitude would be commendable did this scepticism 
stimulate inquiry and not serve to bar the way to further investigation on the 
part of those by whom it had been assumed. 
An instance of such state of mind with the possible occurrence of the latter 
contingency haying already occurred with reference to the above proposition 
regarding hybridisation and inoculation, it may not therefore be amiss to 
briefly set forth some of the grounds for recommending resort to these pro- 
cedures in the preventive treatment of plant diseases. 
: HYBRIDISATION AND CROSS-FERTILISATION, 
It is universally admitted that plants that are in a vigorous condition are 
less prone to the incursion of disease than are such as are constitutionally weak, 
when both are being grown under identical circumstances. And it has been 
demonstrated by the late Charles Darwin, and accepted as a law by all naturalists, 
that cross-fertilisation is necessary for the production of vigorous offspring. As 
the outcome of years of research, Darwin proved that by cross-fertilisation plants 
were obtained which—as compared with others not cross-fertilised—exhibited not 
only increase in height, weight, and fertility of offspring, but also greater con- 
stitutional vigour. Moreover, this latter was manifested by the development of 
@ special “innate power of the crossed plants to resist unfavourable conditions 
of growth,” and in the fact that they died prematurely “ independently of 
any innate cause that could be detected” far less frequently than did plants 
that were not crossed.* And he also found that “the good effects of cross- 
fertilisation were transmitted by plants to the next generation,” and in some 
instances “to many succeeding generations.”> : 
One of the ablest vegetable pathologists has thus expressed himself on the 
subject of breeding plants and the occurrence of plant disease ae A. number 
of the problems connected with the subject [Evolution of Parasitic Fungi] are 
suggested in the discussion of the various paragraphs: [of the address}, and the 
solution of these questions require not only the investigations of the mycotogist 
but also of the practical fruitgrower. Propylactic treatment, no doubt, must 
be depended on ina great many cases ; but in many others, by careful attention 
to the breeding of healthy, stocky, and resistant varieties of fruits and other 
plants, to this extent shall we be able to dispense with the knapsack sprayer. 
Bir One of the important problems is the development and fixing of 
disease-resisting varieties. f : 
C. Darwin : “Cross and Self Fertilisation of Plants,” Chap. VII., 1876. 
+ Op. cit., p. 488. ' . Ree 
+G, F. Atkinson: “Some Tendencies and Problems in the Evolution of Species of Parasitic 
Fungi.” ‘Transactions, Massachusetts Horticultural Society, 1896. 
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