No. 4, February, 1922] PATHOLOGY 289 



1885. QuANJER, H. M., EN J. O. BoTJES. L'enroulement des feullles (leptonecrose) et 

 la frisolee (mosaique) de la pomme de terre. [Leaf-roll and curly dwarf potato.] Ann. 

 Sci. Agron. Frangaise et Etrangere 36: 262-280. 1919. — riiloem-necrosis (leaf-roil) and 

 mosaic (including curly dwarf) are entirely sinailar in their mode of propagation. Infection 

 does not arise from the soil. — Botjes is credited with the discovery of the method of dispersal 

 in the field and of the method of culture to free stock from disease. Quanjer discovered 

 phloem-necrosis in 1908 and described it in 1913 after being convinced of its diagnostic value 

 for detecting leaf-roll. Leaf-roll, or phloem-necrosis, is contagious and pseudo-hereditary, 

 characteristics which enable it to be distinguished from temporary leaf-roll caused by soil 

 influences. It is also characterized by necrosis of the phloem bundles, thus differentiating 

 it from diseases of the woody vessels. Plants inoculated with the mosaic virus show the first 

 symptoms of mosaic in their offspring, and in the 2nd or later generations an aggravated form 

 of curly dwarf appears. The 2 diseases are similar in that they are scarcely discernible in 

 the year in which infection occurs. In general, phloem-necrosis develops more rapidly in 

 succeeding generations than does mosaic. — Contagiousness of the 2 diseases was proved by 

 grafting diseased tubers on sound ones. Pot experiments in which diseased and sound tubers 

 were in some cases planted together, in others separated, and in which the tops of the plants 

 were or were not separated by glass, have shown that in general the diseases are carried through 

 the soil, only rarely through the air. Botjes' observations tend to show that the phloem- 

 necrosis organism does not winter as a saprophyte in the soil, but is carried by the tubers, 

 and that cases of contagion attributed to soil are due to carriage of the virus — limited to a 

 distance of about 20 m. Inasmuch as the organic union of roots is not verified, it is possible 

 that the virus may live for some time in the soil. Whether root wounds are necessary for 

 infection has not been ascertained. — Experiments show that mosaic passes from tobacco to 

 tomato, and reciprocally, and from tomato to potato, but not from tobacco to potato. — 

 Starch-staining experiments show that the virus of mosaic and similar maladies ascends with 

 the sap and that the infectious matter of phloem-necrosis is carried by the phloem. The 

 so-called senility of certain potato varieties is explained by the fact that these 2 diseases, 

 considered as symptoms of degeneration, and propagated by means of tubers, become in- 

 tensified with long culture. It is possible that the virus adapts itself gradually to varieties 

 which are at first very resistant. — The basic principle of control methods is the use of an 

 isolated plot for seed production and careful inspection of growing plants. — A. B. Beaumont. 



1886. Ramirez, RomXist. El chahuLstle rojo del frijol. [Rust of the bean.] Rev. Agric. 

 [Mexico] 5 : 830. 1921. — This is an account of Uromyces appendiculatus on the common bean. — 

 J. A. Stevenson. 



1887. ScHULTZ, E. F. La "Rhizoctonia violacea" en los alfalfares de Tucxmian. [Rhizoc- 

 tonia violacea in the alfalfa fields of Tucuman.] Rev. Indust. y Agric. Tucuman 10: 154-182. 

 4 fig- 1920. — The short duration of alfalfa fields in Tucuman (3-5 years) is generally attrib- 

 uted to weeds, such as Cynodon dactylon and Holcus halepensis. Weeds, however, are easily 

 controlled. Other causes are tramping by cattle in wet seasons, excessive moisture, poor 

 drainage, lack of lime on acid soils, over-cutting, and over-pasturing. The greatest losses, 

 however, are due to Rhizoctonia violacea, which attacks the main root 2-3 inches underground. 

 The factors given above all tend to weaken the host plants and bring about fungus attacks. 

 Diseased plants turn yellow and finally die, leaving bare spots, which soon are occupied by 

 weeds. Other crop plants are susceptible and sweet potatoes in particular should not be 

 used in rotation with alfalfa. The disease can be controlled by careful preparation of the 

 soil, liming, and soil inoculation with legume bacteria. Other crops should not be inter- 

 planted with alfalfa. — John A. Stevenson. 



1888. ScHULTZ, E. S. A transmissible mosaic disease of Chinese cabbage, mustard and 

 turnip. Jour. Agric. Res. 22: 173-177. PI. B (colored) and 22-23. 1921. — Chinese cabbage 

 (Brassica pekinensis), mustard {B. japonica), and turnip (B. rapa) are affected with a typical 

 mosaic disease. The disease is readily communicated from one plant to another and from 

 one species to another, both by artificial inoculation and by natural inoculation with the aphis 



