1916] DISEASES OF PLANTS. 457 



On bitter pit and sensitivity to poisons, HI, A. J. Ewabt (Proc. Roy. Soc. 

 Victoria, n. ser., 26 (1913), No. 2, pp. 228-242, pi. 1).—Iu pursuance of the 

 work above noted, in which the extreme sensitivity of the apple to poisons 

 was made evident, the author has instituted a comparison between these 

 results and those obtained by studies with potatoes, which are also capable 

 of prolonged semidormant existence and which also become discolored by 

 oxidase action when dead, but which, unlike apples, are capable of further 

 gi-owth after being injured. 



It is stated that, in all cases, potatoes are less sensitive to poisons than are 

 apples, differences in resistance varying from 1,000 times with anesthetics to 

 S or 10 times with alkali and copper sulphate. Mercuric chlorid and copper 

 sulphate are about equally poisonous to potatoes. Sulphuric acid, while 

 slightly less poisonous than lead nitrate, is about 50 times as poisonous as 

 alkali. Potatoes, like apples, are much more sensitive to poisons at high than 

 at low temperature. 



Tannic acid precipitates starch from its aqueous solution. The occasional 

 starch grains found in apples which are resistant to hydrochloric acid are 

 thought possibly to have been in contact with the tannic acid of the cell sap. 

 The presence of from 0.0003 to 0.003 per cent of tannic acid distinctly retards, 

 0.003 to 0.06 per cent strongly retards, and 0.33 to 1 per cent practically in- 

 hibits diastatic action, this effect showing at 35° C, and being more pro- 

 nounced below 20°. The cell sap of apples may contain as much as 0.1 per 

 cent tannic acid, and bitter pit tissue appears to contain more than does nor- 

 mal pulp. This will protect any starch grains extruded into the cell sap 

 from solution, and in cells bruised during the starch stage, will aid in pre- 

 venting the starch from dissolving. In the bitter pit cells, however, the starch 

 grains are in the protoplasm, and as long as this is living the tannic acid of 

 the cell sap is not in contact with them or with diastase. Diastase solution 

 loses its solvent action after prolonged contact with pulp of pounded apples. 



It is considered as very desirable that a complete numerical analysis of 

 the mineral constituents of bitter pit tissue in bulk be made, paying special 

 attention to metallic elements in small amount, for the purpose of definite 

 guidance for further investigation. 



Bitter pit and sensitivity of apples to poisons, H. G. Bbeidahl and A. C. H. 

 RoTHERA (Proc. Roy. Soc. Victoria, n. ser., 27 (1914), No. 2, pp. 191-197). — 

 Replying to the claims of Ewart above noted, referring to investigations show- 

 ing an accelerating action of malt diastase, the authors hold that his tannic 

 acid complications are not applicable to the experiments which he discusses, 

 that his assignment of the tannic acid retardation to an action upon the starch 

 is incorrect, and that his experimental results were obtained under conditions 

 and with proportions of reagents entirely different from those in experiments 

 which he criticizes. 



On bitter pit and sensitivity of apples to poison, IV, A. J. Ewakt (Proc. 

 Roy. Soc. Victoria, n. ser., 27 (1914), No. 2, pp. 3^2-3^9).— Replying to the 

 observations of Rothera and Breidahl above noted, and also to criticisms at 

 the September meeting of the Royal Society of Victoria, the author states that 

 an accelerating action may be obtained if a resistant and very active diastase 

 be used in large amount, if the tests are made at high temperatures, and if dry 

 bitter pit pulp in which the tannic acid has been oxidized is compared with 

 fresh pulp rich in tannic acid. Results of his own more recent tests are given 

 and claimed to coincide closely with those which he has previously published. 



The control of peach leaf curl, A. S. Horne (Jour. Roy. Hort. Soc, 41 

 (1915), No. 1, pp. 110-114, fig- 1). — This is an account of tests made at the 



