PRESIDENTIAL ADDRESS. 829 



how to cultivate them.' '" As we have already seen, Biffen and others have shown 

 that under certain conditions the quality inherent in some varieties to resist 

 disease may be utilised to great advantage. The national importance of such 

 work is impressed upon us by the enonnous losses sustained every year by rust 

 in wheat, mould in hops, and the widespread disease of potatoes. One of the 

 most striking instances in recent times was the destruction of the valuable 

 coffee plantations in Ceylon. The industry, an exceptionally valuable one, 

 was wiped out in a com.paratively few years by the coffee-leaf disease (Hcmileia 

 vastatrix). In the light of our present knowledge it is not improbable that 

 this disease may have been checked by seed selection or raising an immune 

 race of plants. Or, more probably, as suggested by Armstrong, by regulating 

 the use of essentially nitrogenous manures, which are known in some cases 

 to intensify the attacks of fungoid pests, and substituting the use of phosphates. 



In the Malay States the life history of some of the more prominent diseases 

 of rubber trees has received close attention. Fames lignosus, a root fungus, 

 is local in character, and as its effects quickly appear there is time to take 

 remedial measures before the neighbouring trees are affected. Ustvlina zonata, 

 causing collar-rot, on the other hand, is slow in action, and therefore all the 

 more dangerous. A third rubber disease. Fames pseudo-ferreus, spreads 

 entirely by the contact of the roots with diseased jungle stumps or roots of 

 other diseased rubber trees. As remedial measures are impossible in this 

 instance a clean-clearing policy is being vigorously advocated, and under scientific 

 advice this may become the rule on all young i-ubber estates in the East. In 

 this country Salmon, who is undertaking a detailed study of the hop mildew 

 {Spharatheta humili), has obtained seedlings which he states 'have retained 

 immunity after four years' trial in a hop garden under normal conditions of 

 cultivation and manuring.' As the depredation of mildew, commonly known as 

 mould, causes great loss to hop growers, the research work carried on by Salmon 

 is watched with great interest. Progress is necessarily slow, but a hop immune 

 to mould would be a valuable acquisition in hop-growing districts. In the 

 successful treatment of the diseases of plants the field of work in the Empire 

 is realised as practically without limit ; but it is one in which advance must be 

 made by the development of pure science, and by men with a broad outlook 

 and fully in touch with the practical as well as the scientific side. 



As illustrating the occurrence of an incidental result arising from a purely 

 scientific investigation, mention may be made of the discovery of a remarkably tall 

 strain of flax at the John Innes Institution. This, if capable of being estab- 

 lished on pure lines, may prove of economic value. It is a hopeful sign that the 

 appreciation of the work done at this institution, under the stimulating energy 

 of Bateson, is increasing day by day. The broad-minded interpretation that has 

 been placed on the generous bequest made by Mr. Innes and the recognition 

 of the fact that an accurate knowledge of heredity must form the basis of the 

 bulk of the new work in horticultural breeding are full of promise. We have, 

 further, the assurance that recognition will be given to the principle that if 

 progress is to be made theory and practice must be closely interwoven. Amongst 

 other important investigations undertaken at the John Innes Institution, Miss 

 Ida Sutton has recently published a Report on Self-sterility in such fruit-trees 

 as plums, cherries, and apples. It has been recognised that failure in fmxt 

 crops is not infrequently due to self-sterility. Two main questions were dealt 

 with, (1) whether self-sterility is a simple Mendelian recessive character, and 

 (2) whethev self-steriles are fertile with the pollen of any other variety. So 

 far, with regard to (1), the results show there is nothing which negatives the 

 view that the property of self-steril'ty may be recessive, and in regard to 

 (2) what East has called ' cross-incompatibility ' is not confirmed by Miss 

 Sutton's researches. The general conclusions arrived at by Miss Sutton are : 

 (a) that many important commercial varieties of fruit trees set little or nothing 

 unless cross-pollinated ; (6) that for the pollination of these self-sterile kinds 

 pollinisers must be planted ; (c) that provided a variety produces plenty of 

 pollen and flowers simultaneously with the variety which is intended to pollinate, 

 any variety, at least of plums and apples, will probably serve for this purpose, 



" Science and the Nation. 118. 



