DISEASES OF PLANTS. 347 



The leaf curl of potatoes, P. De Caluwe (Handel. Vlaamsch Natuur en 

 Geneesk. Cong., 12 {190S), No. 2, pp. 195-200). — A description is given of tlie 

 leaf curl of potatoes, a disease which has become quite prevalent and destruc- 

 tive in Germany, Holland, and elsewhere. 



Notes on the leaf roll disease of potatoes, O. Appel (Jahresber. Ver. Angeio. 

 Bot., 6 {1908), pp. 259-265). — An account is given of a leaf roll disease of 

 potatoes, and the author states that probably several forms of disease are con- 

 fused in this term. In 1905-6 a species of Fusarium was commonly found in 

 diseased tissues, while in 1907 and also in 1908 Verticillium albo-atnim was 

 present in the diseased stems. He thinks that this disease, instead of being of 

 recent occurrence, has been Imowu for some time, and states that there is evi- 

 dence that it has been recognized for more than a century. 



The leaf roll of potatoes, Schleh {FUhUng's Landic. Zig., 58 (1909). No. 

 18, pp. 6Jt 1-663). — The author has carried on several years' observation and ex- 

 perimentation witli this disease, seeking methods for its control. He concludes 

 that the various forms, such as stunted growth, leaf curl, and crinkled leaflets, 

 are all due to the same cause, the specific nature of which has not been posi- 

 tively determined. The disease is readily transmitted through the tubers, and 

 its virulence seems to increase from generation to generation. 



Fertilizers do not seem to influence the disease to any considerable extent, 

 although some methods of culture seem to favor its development. Poorly devel- 

 oped tubers are more likely to spread the disease than sound ones. There is 

 little evidence thiit the cause of the disease can be transferred from the tuber 

 to the soil, yet as a precaution rotation of crops is advised. 



The usual methods for combating plant diseases are said to have failed, and 

 the author advises extensive experiments by potato growers to ascertain prac- 

 tical methods for the control of this trouble, which he states is becoming one of 

 the most serious of potato diseases. 



Internal brown rot (Jour. Bd. Agr. [London], 16 (1909), No. 8, pi). 6.'/7, 

 648). — A description is given of the internal brown rot or sprain of potatoes, the 

 precise nature of which is obscure. In some specimens mycelium was found in 

 the tissue of the brown spots, and under proper conditions the winter rot 

 caused by Xcctria solani always developed. In other cases no mycelium could 

 be found, nor did any fungus develop even under favorable conditions. 



Tubers showing this disease were planted, and every tuber produced showed 

 the presence of small spots, indicating that the disease is transmitted from 

 seed tubers to the following crop. Where there were no signs of winter rot on 

 the tubers planted the sets produced a perfectly clean crop. 



A preliminary account of this disease, suggesting a possible cause, has been 

 noted elsewhere (E. S. R., 21, p. 447). 



Sugar beet and potato diseases in 1908, A. Stift (Centbl. Bakt. [etc.], 2. 

 AM., 2.3 (1909), \o. 6-9, pp. 17.3-192). — A critical review is given of some of 

 the more important contributions in 1908 relating to the diseases of sugar beets 

 and potatoes, about 100 publications being considered. 



The root rot of beets and its control, E. Riehm (B1. Zuckerriibenhau, 16 

 (1909), No. 10, pp. lJi5-lJt9). — An examination of a large number of diseased 

 beets is said to have shown the presence of 3 fungi, Phoma bette, Pythiiim 

 debaryanmn, and Aphanomyces Iwvis, all of which from the nature and abun- 

 dance of their occurrence must be considered parasitic. 



Of the species observed the Phoma was found to be distributed through 

 pycnidia on beet seed. The other fungi are soil organisms that attack the 

 roots in the field. The disease is said to be primarily one of young beets and 

 anything that tends to check their growth will make them more susceptible. 



