430 EXPERIMENTAL FARMS 



4 GEORGE V., A. 19H 



(Miti rely to the investigation of tins problem. Mr. McAlpine's first report on the work 

 done now lies before us in tbc shape of a handsome quarto volume,* containg some 200 

 pages of text and descriptive letter press, and 35 plates with 133 illustrations of great 

 excellence, mostly from origin;;; photographs. The work summarized included a 

 detailed histological study of the Pome fruits, particularly with respect to the vascular 

 system, the characteristics of the disease, a critical review of the literature on the 

 history, distribution and hypotheses advanced in explanation of its occurrence, an 

 analysis of the replies to a series of questions submitted to growers regarding more 

 particularly the contributing factors, and an outline of experiments carried out and 

 in progress. It is impossible to attempt in this place an adequate review of the 

 phases of work taken up, but a few of the more interesting points may be noticed. 



The form of the disease termed 'crinkle,' or confluent bitter pit, which is 

 characterized by the surface of the fruit being thrown into rough folds with large 

 cavities in the underlying tissues, is new to us, and according to the author has 

 apparently been recorded outside of Australia only from California. 



As regards the causes of the trouble, Mr. McAlpine considers that the evidence 

 is entirely in favour of the hypothesis that it is due to irregularities in the factors 

 influencing the balance between transpiration and water supply, and not to poisoning 

 of cells, e.g., by arsenical sprays. Both the recorded history of the disease and its 

 presence on unsprayed trees are against the latter hypothesis. It was also found 

 experimentally that fruit of an unsprayed tree protected from any possible contact 

 with spray material from other parts of the orchard by being enclosed in calico bags 

 as soon as the fruit had set was quite as badly affected as the exposed fruit of the 

 same tree. The author sums up the matter of poisoning from the exterior as follows : — ■ 

 ' After testing the effects of various chemical substances applied to the skin of the 

 apple, I cannot emphasize it too strongly that all this production of external spots and 

 smears has nothing to do with Bitter Pit. This disease originates from within and 

 the action of an external agent on the skin is something totally different.' 



The principal contributing factors are given as follows : — 



' 1. Intermittent weather conditions, when the fruit is at a critical period 

 of growth. 



' 2. Amount and rapidity of transpiration. 



' 3. Sudden checking of the transpiration at night when the roots are still 

 active owing to the heat of the soil. 



' 4. Failure of supplies at the periphery of the fruit followed by spasmodic 

 and irregular recovery. 



' 5. Irregularity of growth, so that the vascular network controlling the 

 distribution of nutritive material is not regularly formed. 



'6. Fluctuations in temperature when fruit is in store, and 



' 7. Nature of variety.' 



The question of storage conditions is particularly important since the disease 

 usually develops to a large extent in storage. It was found, however, that ' even with 

 very susceptible varieties the development of Bitter Pit was retarded by keeping them 

 at an even temperature of 30° — 32° F.' It is recommended 'that the apples should 

 bo picked .... just when they have reached their full size, and on the green side, and 

 placed in cold storage without delay.' 



We congratulate Mr. McAlpine on the work he has already accomplished and 

 shall look forward with increased interest for the results of his experiments directed 

 towards the control of the trouble in the growing fruit. 



* Bitter Tit Investigation. Tlie past history mvH present position of the Bitter Pit 

 quest ion, by D. McAlpine. First Progress Ivi port 1911-12. 



