DISEASES OF PLANTS. 671 



A potato disease known as blackleg, of bacterial origin, is prevalent in Europe, bul 

 is not as yet know n to occur in this country, and while varietal resistance to this dis- 

 ease is not hilly established, it seems thai certain thick-skinned varieties rich in starch 

 are more resistanl than the thin-skinned ones with a low starch content. 



The late blight, or rot, due to Phytopkthora infestans occurs more commonly in 

 Europe than iii America, and the principal investigations have been on the resistance 

 to this disease. It seems from the information al hand that disease resistance is :i 

 relative characteristic, qo variety being wholly proof againsl the blight or rot. It 

 seems t«. be related to the general vegetative vigor of the plant, and in some instances 

 resistance may be acquired by originating new varieties, hut all seedlings will not 

 show superior disease resistance. 



It is believed that some of the wild specie- of tuber-bearing Solanums offer promise 

 for hybridization, hut as yet qo practical results have been secured. The possibility 

 of disease resistance being established by selection has not been proved, and it is 

 said that early varieties may escape the disease by maturing before it becomes epi- 

 demic, hut when similarly exposed they are as a <-las< less resistanl than late varieties. 

 The source from which ^n^l tubers is obtained is -aid to be a matter of importance, 

 northern-grown seed giving plants of superior resistance in Europe, and possibly 

 tubers are better for seed purposes if they are dug before they reach full maturity. 

 High fertilization, especially with nitrogenous manures, lower- the power of tin- plant 

 to resist blight and rot, and red varieties with thick, rough skin and relatively high 

 starch content are usually more resistant than the thin-skinned white varieties, 

 which are richer in protein. 



So far as stem and foliage characters are concerned, the evidence favors varieties 

 that have hard, rough, woody stems and small, rough, dark-colored leaves. In 

 England the Evergood, Discovery, Royal Kidney, Northern Star, Sir. John Llewelyn, 

 King Edward VII, Eldorado, and Eactor are rated high as to disease resistance, 

 while in Germany and Holland the best types are Mohort, Irene, < ieheirnrat Thiel, 

 Professor Wohltmann, Boncza, Eigenheimer, and Paul Kri'iger. 



In this country trials as to disease resistance have been carried on at a number of 

 the experiment stations, notably at the Vermont Station, where breeding and selec- 

 tion experiments for increased resistance are under way. In this country no variety 

 seems especially preeminent in resistance, but Dakota Red, Rustproof, Irish Cobbler, 

 Sir Walter Raleigh, Doe Pride, and White Beauty deserve mention as of the resistant 

 class. 



The evidence at hand seems to justify the hope that by the coordinated effort- of 

 potato specialists it will be possible to develop varieties of potatoes combining gen- 

 eral excellence with a high degree of resistance, and the author urges all interested 

 to aid toward the accomplishment of this end. 



Club root disease of swedes and turnips, 1). A. Gilchrist ( Count)/ Xorthumb., 

 Ed. Com., Bul. S t j>j>. 08-48, figs. 8).— A description is given of club root of crucif- 

 erous plants and a record presented of experiments which have been carried on to 

 test the effect of different dressings to check the disease. A short account of the 

 fungus which causes the disease is also given. 



In the experiments for the control of the disease varying amounts of lime were 

 employed at different dates, and on the whole it was found that the application of 

 lime to be most efficient should he made a considerable time in advance of the sow- 

 ing of the crop. In some of the plats the best results were obtained where from 1£ 

 to 2£ tons of lime were applied 2 years before seeding. In the most extended series 

 of experiments, which covered several years' observations, the best result- were 

 obtained where 1£ tons of lime per acre were applied to all the plats 4 years before 

 seeding. This treatment resulted in a considerably increased total yield and a 

 greatei freedom from disease. 



