DISEASES OF PLANTS. 485 



Some culture experiments with, rust fungi on Um.bellifer8e, O. Semadeni 

 {Cniihl Bakt. u. Pur., 2. Aid., 10 {100S),No. 16-17, jjp. 522-5,?4).—The results of 

 studies of several species of fungi which normally occur in umbelliferous i)laiits are 

 reported. The author found that Puccinia pimpinellx, P. clmrophnUi, and P. petro- 

 .s'('?uh' were auttecious, while .Fjc'idnim mei, P. caribistorix and P. poliigoni riripari were 

 hetenecious, one phase occurring on species of umV)elliferous plants and the other on 

 species of Polygonum. 



Club root of cabbages ( Gard. Chron., 3. ser., 34 {1903), No. 878, p. ;?9-:?).— Accord- 

 ing to the writer's observations the club-root fungus remains alive in tlie soil for a 

 nmch longer pei'iod than has been previously supposed. An account is given of 

 a crop of crucifers on soil that had not carried a similar crop for at least 20 years, 

 having been planted continuously in dahlias, chrysanthemums, and potatoes. 

 The resultant crop was badly infested with club root. Experiments with lime are 

 reported, showing it to be a specific for the jirevention of this disease. 



Club root of cabbages {Gard. Chron., 3. ser., 34-{1903), No. 870, p. 163).— In & 

 brief note the successful use of gas lime for the prevention of club root of cabbages 

 is reported. 



A new cucumber disease, M. C. Cooke ( G^arrf. Chron., 3. ser., 34 {1903), Nos. 867, 

 p. 100; 871, p. 172, fig. 1). — The author describes a disease of recent appearance on 

 cucumber fruits, in which the fungus forms on the surface of the fruit dark depressed 

 spots, which gradually enlarge and become quite black, cracking either across or 

 around and exposing the paler tissues underneath. The organism has not been 

 definitely determined, but it has been provisionally called Cladosporium scabies. 



In a subsequent note the author states that the mycelium evidently permeates the 

 entire fruit, and that every fragment of the infected cucumbers should be collected 

 and burned. If spraying should be undertaken, the author believes that Condy's 

 fluid, diluted, would be less liable to injure the fruits than copper fungicides. 



A cucumber leaf disease {Jour. Bd. Agr. [London], 10 {1903), No. 2, pp. 166- 

 170, pi. 1). — A report is given of the recent observation of a leaf disease of cucum- 

 bers, which in general appearances resembles the ordinary leaf spot of that plant. 

 An examination of diseased material showed, however, that it was caused by an 

 entirely different fungus {Dendrgphivm comosum). 



This disease which, according to the account, is confined to cucumbers grown 

 under glass, appears early in March and attacks the plants while quite young, 

 destroying the tissues of the leaf, and in bad cases also infecting the growing points of 

 the shoots. The fungus is usually recognized as a saprophyte and was probably 

 introduced into the cucumber houses by the manure that was used. So far only the 

 conidial phase has been discovered, but the fungus is still under observation. 



The writer believes that l)y ventilating the houses and securing a drier atmosphere 

 the disease can be greatly restricted, and if necessary spraying the plants with a 

 weak solution of potassium sulphide would prove advantageous. 



Cucumber leaf spot, G. Massee {Gard. Chron., 3. ser., 34 {1903), No. 871, 

 p. 184). — In reply to a correspondent the author gives a description of leaf spot of 

 cucumbers which is caused by Cercospora melonis. For the eradication of the disease 

 it is recommended that the soil in the cucumber house should be disinfected by 

 spraying with fungicides and care should be exercised to prevent too soft a growth 

 of the foliage and the introduction of the fungus from without the greenhouse. 



A mildew of rbubarb, A. Ostekwalder {Centbl. Bakt. n. Par., 2. Abt., 10 {1903), 

 No. 24-25, pp. 775-777, figs. ,?).— The author reports the presence of a species of 

 Peronospora on the variety of rhubarb PJteuin undrdatum. This mildew appears 

 upon the leaves early in the spring, producing small reddish spots, which are more 

 or less limited by the veins. Later the spots increase in size and coalesce, destroy- 

 ing the leaf tissues. 



The author has compared the sjiecies with P. rumicis, which lius been previously 



