DISEASES OF PLANTS. 51 



The work is described at considerable length, frequent references to litera- 

 ture being given, and in i-ondusion a bibliography is appended. 



The effect of Ustilago maydis on Zea mays tunicata, Chifflot (Vfwipt. 

 Rend. Acad. Sci. \l'(irix], I'lS {1909), No. 7', pp. J, 26-.'i29).— For a number of 

 years the author has been growing the variety tunicata of Z. mays in the bo- 

 tanical gardens at I.yon. Two forms were always produced, a tunicate and a 

 naked spike, although seed from the naked form was continuously planted. 

 The planting has been made where corn snuil was abundant, as shown by its 

 occurrence on other varieties, but no ti'auniatisnis have ever been observed on 

 the root.s or young plants of this particular variety. 



If the staminate flower panicles which are attacked by the smut fungus be 

 examined, in the so-called cauliflower clusters there will be found pistillate and 

 hermaphrodite flowers. The anthers of the stamens, although api)arently 

 normal, do not open, or only slightly, and the pollen grains appear greatly 

 modified. Sometimes the filaments are hypei'trophied and the ovules of the 

 hermaphrodite flowers do not mature, but the pistillate flowers always develop 

 and produce seed. None of these modifications are observed in the normal 

 staminate flowers. The change is attributed to unequal osmotic pressure due 

 to the presence of the fungus, producing hypertrophy of the vegetative and re- 

 productive organs. 



Black root disease of cotton in Georgia and its control. A. C. Lewis 

 (Ga. Bd. Ent. Bui. 28. pp. 2.J. fiffs. 9). — A popular description is given of the 

 black root or wilt disease of cotton, due to the fungus Xcocosniospora rasinfccta, 

 and means are suggested for its control. 



The author reix)rts 3 years' experiments for the control of this disease, show- 

 ing that fertilizers, fungicides, and date of planting have little or no effect in 

 reducing it. Variety tests have shown that while different varieties vary greatly 

 in their susceptibility to disease, none except a few resistant strains are suifi- 

 ciently resistant to warrant their planting on diseased land. Among these are 



2 varieties originated by the Bureau of Plant Industry of this Department and 



3 strains not yet named which were originated by the author. 



Potato scab and its eradication, L. F. Henderson {Maritime Farmer, IJ/. 

 (1909), yo. 13, pp. 291, 292). — The results of a series of experiments on the pre- 

 vention of potato scab by means of treating the seed tubers with sulphur, 

 formalin, and corrosive sublimate are given. Different lots of seed were treated, 

 some scabby and others apparently free from disease, and the treated tubers 

 planted in clean and scab-infested soils. 



As a result of the exiieriment, the author found that rolling seed potatoes in 

 sulphur did not prevent scab to any considerable extent. Treated potatoes 

 planted in soil that was scabby from the previous year's crop produced a scabby 

 crop, while treated potatoes planted in scab-free soil gave clean tul)ers. For- 

 malin gave as good results as corrosive sublimate, and being less dangerous to 

 use, is recommended for general use for scab prevention. 



A radish disease, K. von Tubeuf {Xaturw. Ztsehr. Fnmt. v. Landic, 6 

 {1908), A'o. 9, pp. Ji81-.'i92, figs. 7). — In ISOS the author described a bacterial 

 disease of radishes and gave suggestions for its control. Later (K. S. R., 12, 

 p. 462) a disease somewhat similar in gross characteristics was described as 

 due to Peronospora parasitiea. The author has repeated his study of the liac- 

 terial disease, comparing it with that caused by the fungus. The bacterium was 

 again isolated and cultivated on nutrient media and inoculation experiments 

 were made showing that the condition originally described by him was due tti 

 the bacterium. In nature the bacteria probably gain entrance through insect 

 or other injuries and their spread is facilitated by the fungus. Comparing the 

 effect of the bacterium and the Peronospora, the author states that the spread 



