1920] DISEASES OF PLANTS. 47 



ties by the selection of sliallow-eyed seed tubers should be undertaken, accord- 

 ing to the author, with extreme caution. 



Rhizootoiiia disease, or stem rot, on potatoes, D. O. O'Brien {Scot. Jour. 

 Agv., 2 (1919), No. 4, pp. 4S2-491, pis. 8, figs. ^).— In addition to a general 

 account of the rot disease of potatoes caused by R. solani on potato tubei s and 

 also by R. violacea (R. crocorum) on the tuber or stem, a more detailed account 

 is given of this disease, which was found by the author to be widespread in 

 Scotland about two years previous to this report. A large i>ercentage of market 

 potatoes were affected, particularly those from the red soils of Scotland. A 

 bibliography on the subject is appended. 



Certification of stocks of varieties of the potato which are inimnne from 

 wart disease {Scot. Jour. Agr., 3 {1920), No. 1, pp. 52-66, pi. 1). — Recent re- 

 ports show that potato wart disease is more widespread than was previously 

 supposed in England and Scotland, large areas having now been declared in- 

 fected. 



Studies carried out during recent years encourage the hope of developing 

 popular potato varieties immune to wart disease. The certification of seed in 

 sufhcient quantities after growing the crops under rigid inspection is expected to 

 assure a supply of pure stocks of inmiune varieties. Good results have already 

 begun to appear after a trial continuing for two years. This article is mainly 

 concerned with the identitication of rogues and of innnature varieties and the 

 prevention of deterioration from disease. 



Eradication as a means of control in sugar cane mosaic or yellow- 

 stripe, P. S. Eakle (Porto Rico Dept. Agr. Sta. Bui. 22 (1919), pp. i7).— In a 

 previous publication (E. S. R., 41, p. 347), suggestions were given for the con- 

 trol of the sugar cane mosaic which included eradication and the use of resistant 

 or tolerant varieties. In the present publication, an account is given of a year's 

 work on the control of the disease by the method of eradication. Eradication 

 includes the planting only of healthy seed and, when suspected seed has been 

 used, the frequent inspection of the field and removal of all plants showing 

 disease. A survey was made of a number of plantations where this method 

 had been put in practice, and it is lielieved that the cane mosaic or yellow- 

 stripe disease can be controlled in this way in all regions where a supply of 

 healthy seed can be obtained. In regions of complete infection, the establish- 

 ment of healthy seed fields is necessary before a campaign of eradication can 

 be undertaken. 



Root-knot disease of tomatoes, R. Robson (Jour. Roy. Hort. Sac, 44 

 (1919), pp. 31-67, pis. 4)- — Records of experimentation carried out during 

 1915-1917 on tomato subsoils infested with Heterodera radicicola are presented 

 in tabular and other detail, with discussion. This experimentation, carried out 

 under glass, was based on the assumption that the substances to be applied to the 

 soil would inhibit or destroy the nematodes; that such substances if inhibitory 

 to the tomatoes would gradually be carried downward by the processes involved 

 in watering; that a layer of soil impregnated with inhibitory substance would 

 prevent the ascent of the nematodes ; and that the tomatoes would find adequate 

 growth conditions above the poisonous layer. 



It was found that sodium or potassium cyanid applied at half a ton per acre 

 or corrosive sublimate at 3 cwt. will free the subsoil from nematodes at a cost 

 of about £50 per acre. Carbolic acid, while effective, is more expensive. 

 Cresylic acid is more expensive and less effective. Creosote applied pure is 

 useless, though saponified creosotes tend to check nematodes. Several other 

 substances are discussed in this connection. 



Finger-and-toe [in turnips], J. A. Symon (Scot. Jour. Agr., 3 (1920), No. 

 1, pp. 34, 35). — The prevalence of finger-and-toe in turnips in the north of 



