258 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Daffodil Yellow Stripe Disease. By A. P. Goodwin, Miss Currey, 

 and the Rev. J. Jacob {Garden, No. 1794, p. 197, April 7, 1906 : No. 1797, 

 p. 229, April 28, 1906 ; and No. 1800, p. 271, May 19, 1906).— These 

 articles contain the opinions of expert growers upon this troublesome 

 malady which attacks daffodils, and much useful information is imparted. 



E. T. C. 



Date Varieties and Date Culture in Tunis. By T. H. Kearney 

 {U.S.A. Dep. Agr. {Bur. PI. Inch), Bull. 92 ; September 1906, pp. 110; 

 52 figs. ; 10 plates). — An excellent paper, giving full details of the charac- 

 teristics of the region where the dates are cultivated and the methods 

 employed, together with outline drawings of the various varieties which 

 are fully described, and a key given by which the varieties may be 

 recognised. — F. J. C. 



Davidia involucrata. By Anon." {Gard. Chron. No. 1014, 

 p. 346, fig. 138 ; June 2, 1906). — A very interesting tree belonging to 

 the Cornel family, comparatively lately introduced into cultivation from 

 China, and flowered for the first time in Europe by MM. de Vilmorin, who 

 supplied the photograph from which the figure was made. It is said to 

 be quite hardy. It is chiefly remarkable for the large cream-coloured 

 bracts w^hich surround the relatively inconspicuous flowers. The germi- 

 nation of the seeds presents some interesting feg^tures, which were 

 described in the Journal of the Linnean Society (June 18, 1903, p. 556) 

 by Mr. Hemsley. — G. S. S. 



Diseases due to Physiolcg-ical Causes. By G. E. Stone {U.S.A. 

 Exp. Stn. Mass., 11th Ann. Bep. 1905, pp. 31-34). — Gives a useful 

 list of diseases &c. of plants not generally regarded as caused by insects or 

 fungi, but due to physiological causes. — F. J. C. 



Drug" Plant Cultivation, Progress in. By R. H. True {U.S.A. 

 Dep. Agr., Year Book 1906, pp. 533-540 ; 3 plates). — Many drug plants 

 are found wild in the States, and some through the rapacity of collectors 

 are threatened with extermination. A plea is entered for the utilisation 

 of many of those plants which have valuable properties, but are at present 

 considered only as noxious weeds, and it is pointed out that millions of 

 dollars are sent abroad annually to pay for drugs grown under conditions 

 similar to those obtaining in parts of the States. The following plants 

 are suggested as desirable subjects of experimental culture : — Golden seal 

 {Hydrastis canadensis L.) ; cascara sagrada tree {BJiamnus Purshia^ia 

 DC.) ; Seneca snakeroot {Polygala Senega Linn.) ; purple coneflower 

 {Brauneria [Echinacea] angustifolia Heller) ; American wormseed 

 {Chenopodium anthelminticum Linn.) ; jimson weed {Dattira Stramonium 

 Linn.) ; poke {Phytolacca americana Linn.) ; dock {Bumex crisjnis L.) ; 

 burdock {Arctium Lappta Linn.) ; poppy {Papaver somniferum Linn.) ; 

 camphor; liquorice; belladonna {Atropa Belladonna Linn.); foxglove 

 {Digitalis purpurea Linn.) ; peppers.— i^. J. C. 



Electrical Potential, Influence of, on the Growth of Plants. 



By N. F. Monahan {U.S.A. Exp. Stn. Mass., 11 th Ann. Bep. 1905 

 pp. 14-31). — The experiments were designed to ascertain the influence of 



