NOTES AND ABSTRACTS. 



409 



Potash in Soils, The Effect of Gypsum on the Solubility of. By Paul R. 

 McMiller {Jour. Agr. Res. xiv. No. 1, July 1918, pp. 61-66). — Various soils in 

 Minnesota when mixed with 1 per cent, gypsum, and raised to a point approxi- 

 mating the moisture equivalent and kept for three months, showed a marked 

 increase in the content of water-soluble potash. The results of the experiments 

 depend upon the conditions of contact between the soil and the gypsum. 



A short bibliography is appended. — A. B. 



Potato, Blaekheart in. By F. C. Stewart and A. J. Mix {U.S. A . Dep. Agr., Exp. 

 Stn. New York, Bull. 436, June 191 7, pp. 321-362 ; 10 plates). — Our present 

 knowledge of blaekheart disease in potatos was first made by Bartholomew, 

 who proved that this occurs when the tubers are exposed to a temperature of 

 38-45 0 C. for 14 to 48 hours and that it is due to changes in the tissues due to 

 imperfect respiration. By excluding the air from potatos, blaekheart may be 

 produced at temperatures much lower than those stated above. Numerous 

 experiments have been made by placing the tubers in sealed jars for various 

 periods of time, and it is noticed that when the tubers are exposed to the air 

 the moist surface turns brown, and the " flesh " changes from white to pink and 

 finally to black. Tubers confined in sealed jars with less than ten times their 

 volume of air are unable to do more than sprout. Different tubers show 

 differences in susceptibility both to blaekheart and surface discoloration. 

 Tubers when deeply piled behave in a way similar to those deprived of air in 

 sealed jars. They sprout feebly, become moist on surface, and are affected by 

 blaekheart. They are usually attacked by bacteria and fungi. The authors 

 state that the injury following insufficient aeration is due to lack of oxygen rather 

 than to the accumulation of carbon dioxide. The prevention of blaekheart is a 

 storage problem. — A. B. 



Potato Cultivation. By Nanot and Scribaux {Le Jard. vol. xxxii. p. 287). — 

 Hendrick's proposal to grow potatos in 10 superimposed layers alternating 

 with rich soil, enclosed in a wooden box or frame 8 ft. cube, yields very un- 

 satisfactory results. The difficulty of maintaining a suitable degree of moisture 

 throughout the whole .mass is obvious. 



E. Rousseaux {ibid. p. 302), after numerous experiments, condemns the method, 

 and C. Dumur (p. 303) found that it led to failure. — S. E. W. 



Potato Diseases. By D. C. Babcock (U.S.A . Dep. Agr., Exp. Stn. Ohio, Bull. 319, 

 pp. 119-136; 9 figs.). — The bulletin gives a general account of the commoner 

 diseases of the potato, and details directions in controlling their ravages in Ohio. 



For convenience the diseases are classified under three heads as follows : 



(i) Diseases controlled by selection of clean " seed " tubers : (a) Dry Rot 

 {Fusarium Wilt), (b) Black-leg, (c) Potato Leaf -curl. 



(ii) Diseases controlled by treating " seed " tubers : {a) Potato Scab, (6) 

 Rhizoctonia. 



(hi) Diseases controlled by spraying : (a) Late Blight, (b) Early Blight, (c) 

 Leaf -tip Burn. — A. B. 



Potato Forcing. By H. Blin {Le Jard. vol. xxxii. p. 270). — Seed potatos 

 with not less than two eyes are pressed on the surface of well-tilled ground and 

 covered with a bed of straw, leaves, and grass, 4 or 5 inches deep, which is kept 

 moist, but not saturated with water. When the foliage of the plants begins to 

 fade, the covering containing the tubers is removed. — S. E. W. 



Potato, Fusarium Blight of. By H. G. McMillan (U.S.A. Jour. Agr. Res. 

 xvi., No. 11, March 1919, pp. 279-303; 5 plates). — Three general stages of 

 the Fusarium blight are recognized : (1) The decay and death of the seed 

 tuber before the shoot emerges from the ground ; (2) the attacked seedling which 

 shows the various symptoms of infection ; (3) the mature stage, usually attacking 

 plants of mature growth with infection and decay of the new tubers. Different 

 varieties of potatos show marked variation in resistance to the disease. Two 

 methods of infection are recognized : infection from the soil of roots and root 

 hairs, and infection of the seed tuber. 



The methods of control are : (1) Selection for disease resistance ; (2) superior 

 cultural conditions for the potato plant ; (3) the use of whole seed tubers free 

 from wound or injury. 



The last method is suggested as probably the best for control of the Fusarium 

 blight.— ,4. B. 



