13 



by an immense number of extremely fine vessels which distribute the 

 sap throughout the growing fruit, and that owing to the imperfection 

 of some of these vessels near the skin there is not that proper co- 

 ordination between the amount of water received by the apple from 

 the tree and that removed by transpiration, so that extra pressure 

 is exerted by the contents of the cells which then burst. He admits 

 that he is not quite clear as to whether this is the effect or the cause 

 of the disease. 



The attacks of "bitter pit," he says, are most virulent where the 

 sap flow and the transpiration are subject to violent alterations. 

 Hence the disease is traceable in some degree to climate and in some 

 degree to the variety of the apple. 



I need not enter here into the various practical applications of his 

 discoveries, but he notes that varieties vary considerably in their 

 susceptibility to "bitter pit" ; while some varieties are liable in one 

 district, they are fairly free in others. The commercial varieties 

 best suited to the district should be considered in planting out the 

 orchard and a suitable site chosen. 



'Stated generally, excess must be avoided and moderation practised 

 in the various orchard treatments, such as pruning, manuring, and 

 irrigation. Tho object is to maintain as far as possible steady and 

 uniform conditions of growth. 



I will take the other disease, the "crown gall" or "hairy root." 

 Some time last year a consignment of young apple trees was 

 received from Australia, but they were condemned in New Zealand 

 by the Inspector of the Agricultural Department as being attacked 

 by an infectious disease. The consignors and the Australian Agri- 

 cultural Department were naturally annoyed at this. They 

 contended that the disease "crown gall" is not infectious. And so 

 representatives were sent over to try and convince our people that 

 there would be no risk in allowing them to come into the Dominion. 

 The Agricultural Department had recourse to the Professor of 

 Bacteriology at the University of Otago, and cultures were made 

 in his department and under his supervision. Subsequently, Mr 

 Waters, who had studied biology under Professor Kirk at Victoria 

 University College, and bacteriology under the guidance of Professor 

 (Jhornptaloup. took up the subject. He had been in communication 

 with American plant pathologists and received cultures of the or- 

 ganism that is responsible for the "crown gall" for comparison 

 with those in the imported plants. He established the fact that here 

 too, as in America, the disease is infectious, that it will attack not 

 only apple trees but other plants that if the bacteria get into a 

 wound the disease makes its appearance in a few weeks. 



Incidentally, I may mention that while at Dunedin Mr. Waters 

 has turned his attention to another important matter. He has been 

 able to make cultures of the bacterium which constitutes the essen- 

 tial feature in the "starter" used in cheese-making. Hitherto, as 

 you may be aware, these starters have been imported from Europe 

 in the form of powders, and they have not always been quite satis- 

 factory or reliable owing to the length of time they have been in 

 stock and from other causes. But Mr, Waters has been providing 



