19161 DISEASES OF PLANTS. 349 



new smut fnnj?us is described under tlie name Ustilago arrhenatheri, in con- 

 nection witli abnormalities produced thereby on the host, A. elatius. 



Studies on the dying out of pepper vines in the Dutch East Indies. — I, 

 Summary of previous investigations, A. A. L. Rutgkrs (Dcpt. Landb., Nijv. 

 en Handel [Dutch East Indies^, Meded. Lab. Plantenziekten, No. 18 {1915), pp. 

 2S). — A general survey is given of pepper culture in the Dutch East Indies, 

 more particularly of pepper diseases of economic importance, with special 

 mention of results reported by some investigators in this and neighboring 

 regions. Mention is made of a wilt disease associated with the presence of 

 a fungus in the wood vessels. In some regions nematodes have been found 

 in the roots of the plant. The connection between the above mentioned para- 

 sites and the losses associated therewith has not yet been determined. Results 

 obtained from studies at the government farm at Taliperamba (Madras) 

 emphasize the importance of the method of manuring and cultivating in con- 

 nection with the premature dying of pepper vines. 



Bacterial rot of stored potato tubers, C. M. Hutchinson and N. V, Joshi 

 (Mein. Dept. Agr. India, Bact. Ser., 1 {1915), No. 5, pp. 113-135, pis. 5).— It is 

 stated that four species of bacteria are found to be concerned in the rotting 

 of potato tubers in India. One of these, numbered but not named, is invariably 

 present in the rotting tubers examined. Infection takes place from without, 

 differing in this respect from that due to Bacillus solanacearum. Preventive 

 measures include the avoidance of mechanical injury in handling, storing in 

 dry, coarse sand after immersion in 2 per cent copper sulphate solution with 

 subsequent drying and periodical inspection to prevent infection of sound tubers. 



A pathological and physiological study of the black heart of potato tubers, 

 E. T. Bartholomew {Centbl. Bakt. [etc.}, 2. Abt., 43 {1915), No. 19-24, PP- 609- 

 639, pis. 3).— The author's preliminary studies (E. S. R., 30, p. 149) have been 

 followed up by further studies of the injury and its causation. 



It is stated that black heart of potato is produced, not by a parasitic organ- 

 ism but by abnormal physiological changes. It may be produced artificially 

 by subjecting the tubers to a temperature of from 38 to 48° C. (100.4 to 118.4° 

 F.), the optimum being 42 to 44°, and the optimum period of time being 15 to 

 20 hours. All of the 16 varieties experimented with proved to be susceptible 

 to this trouble, which may be prevented by supplying sufficient oxygen during 

 the period of heating, for which purpose a constant stream of air is not suffi- 

 cient. The tissues do not blacken if the potatoes are kept in an atmosphere 

 devoid of oxygen after removal from the oven. Affected tubers, if not cut 

 open, form after seven to ten days an increasing hollow in the center due to 

 the shrinkage of the tissue. This can not be detected from an outside view. 

 The colors produced, which range from light pink to coal black, are thought to 

 be due to the presence of an oxidizing enzym, tyrosinase, and a chromogen, 

 tyrosin, which interact in the presence of free oxygen and are found in both 

 normal and abnormal tissues of the potato tubers. The amino acid content 

 increases greatly during the period of heating. The discoloration is said to be 

 due to the presence of a substance known as melanin or humin. 



The formation of black heart may be prevented by proper ventilation and 

 the maintenance of a temperature not above 35°. 



Late potato blight in Iowa, A. T. Eewin {Iowa Sta. Bui. 163 {1916), pp. 

 286-306, figs. 8). — The result is given of an investigation of the late blight of 

 potato, particularly with reference to the influence of moisture supply, 

 humidity, and temperature. Three pronounced outbreaks of the late blight 

 are reported to have occurred in Iowa during the past 45 years. These were 

 in 1885, 1903, and 1915. 



