DISEASES OF PLANTS. 449 



Among the diseases described are the crown gall, Are blight, apple scab, black 

 rot, peach yellows, little peach, peach leaf curl, black knot, chestnut blight, and 

 anthracnose of berries. 



Attention is called to the fact that growers frequently heel in stock that is left 

 over, and this becomes a source of many serious infections. The author recom- 

 mends that such stock should be either properly reset or destroyed. 



Crown gall and hairy root, M. T. Cook (New Jersey Stas. Circ. 34, pp. H, 

 figs. 8). — A description is given of cx'own gall and hairy root, most of the 

 information being drawn from other investigators, but the author adds a num- 

 ber of his own recent observations concerning these diseases. 



The circular concludes with a number of suggestions, the observation of 

 which would tend to reduce the occurrence of the disease to a minimum. 



Perithecia in cultures of Venturia inequalis, F. R. Jones (.l&s. in Phyto- 

 pathologij, ^ {1914), No. 1, pp. 52, 53). — The author reports observing perithecia 

 of the apple scab fungus in cultures taken from ascospores in May, 1913, the 

 perithecia appearing in the latter part of November. 



Comparative dusting and spraying experiments, F. M. Blodgett (Ahs. in 

 PhytoiKitlwlogi), 4 {IDI4), No. 1, p. 44)- — Experiments are reported in which 

 a mixture of sulphur and arsenate of lead applied as a powder and also in sus- 

 pension in water as a liquid spray were compared with the regular lime-sulphur 

 solution for the control of apple scab. 



The dustings with sulphur and sulphur in suspension in water were found to 

 control scab to a large extent, closely approximating that of lime-sulphur solu- 

 tion. The control of insects was best effected by the use of the dust sprays, and 

 the apples from this block were considered commercially the best. 



A preliminary report on fruit infection of the peach by means of inocula- 

 tions with Cladosporium carpophilum from peach twigs, G. W. Keitt (Abs. 

 in Fhytopathologg, 4 {1914), No. 1, pp. 49, 50). — The author describes the 

 successful infection of peaches with spores from peach twigs, claiming that the 

 artificial i)roduction of peach scab in this manner has not hitherto been recorded. 



Gum formation in citrus as induced by chemicals, B. F. Floyd {Abs. in 

 Phytopathology, 4 (1914), No. 1, p. 53). — The author tested 28 different organic 

 and inorganic chemicals to determine their affect on gum formation in citrus 

 trees, the chemicals being inserted into the trunk of young budded trees. Thir- 

 teen of the number, including acids, alkalis, and salts of the heavy metals, in- 

 duced the formation of gum in the living tissue bordering that killed by the 

 chemical. The most copious production of gum was induced by copper sulphate 

 and other salts of heavy metals. A microscopic examination showed that the 

 gum originated in the live unlignified xylem tissue, usually in that adjacent to 

 the dead tissue. In the case of gum production by the salts of the heavy metals, 

 gum formation was induced in succulent terminal branches which showed no 

 tissue killed by the chemicals. 



Fungus gummosis of citrus in California, H. S. Fawcett (Abs. in Phyto- 

 pathology, 4 (1914), No. 1, p. 54). — The author states that at least four diffier- 

 ent and distinct gum diseases of citrus trees occur in California— psorosis. mal 

 di gomma, and two forms of lemon gummosis. The latter twjo have been de- 

 scribed (E. S. R., 30, p. 51). A number of other fungi, such as Alternaria citri, 

 Penicillium roseum, Coryneum beycrinckii, and Fiisarium sp., are capable of 

 inducing gum formation when inserted into cuts. The disease, it is said, may 

 be controlled by avoiding the conditions favorable for infection, by making 

 all new plantings with trees budded high on sour stocks, and by trimming out 

 and painting the trunks with concentrated Bordeaux mixture. 



Citrus root nematode, N. A. Cobb (U. 8. Dept. Agr., Jour. Agr. Research, 

 2 (1914), No. 3, pp. 217-230, figs. 13). — An account is given of a study of the 



