DISEASES OF PLANTS. 169 



DISEASES OF PLANTS. 



The origin of parasitism in fungi {Jour. Bd. Agr. [London], 11 (1904), No. 3, 

 pp. 152-154 )• — An abstract is given of a paper by George Massee, in the Philosophical 

 Transactions of the Royal Society of London, on parasitism in fungi. 



It is said that the author has brought to light some of the factors which determine 

 immunity of certain species of plants and individuals to the attack of specific fungi. 

 The investigations seem to show that small differences in the character of the sap of 

 the plants are probably the main determining causes as to whether the fungus shall 

 be able to gain entrance into a plant. As a general rule it was found that, if a weak 

 solution of sugar was introduced within a leaf and spores of any of the commoner 

 parasitic fungi placed on the treated portion of the leaf, the fungus could penetrate 

 and live on the sugar solution, eventually attacking the adjoining tissues. If, on the 

 other hand, a weak solution of acids w a $ introduced the fungus, as a rule, showed no 

 disposition to enter. 



The investigator seems to have been able to cause certain saprophytic fungi to 

 attack living plants, and he concludes that all parasites have developed from sapro- 

 phytes, and it is possible for almost any fungus living on dead vegetable matter to 

 acquire the habit of parasitism. He cites as an illustration the fungus Dendryphiurn 

 comosum, which until recently had not been reported as attacking living plants, but 

 by the aid of unnatural conditions produced under glass houses has been found attack- 

 ing young cucumbers in a very serious manner. 



Recent observations on the loose smut of cereals, E. Schbibaux (Jour. Agr. 

 Prat. , n. ser. , 7 ( 1904 ) , No. 15, pp. 470-482). — A discussion is given of the biology of the 

 loose smuts of cereals, and also the results of the author's observations. He states 

 that the smuts penetrate the wheat plant at 2 different periods, fust during germina- 

 tions and second during the flowering season. The infection during the flowering 

 season is not manifested until the following year. This form of infection is what is 

 called the internal, while the infection which takes place during germination is 

 called external infection. 



For the internal infection the hot- water treatment is said to be the only efficient 

 means, while for preventing external infection other methods are equally as good. 

 The spores of the smut found within the seed are less dangerous to the general 

 crop than those adhering to it, and in cereals where the glumes remained closed, or 

 open for a very short time, the chances for infection are rather remote. This is par- 

 ticularly true if flowering takes place during a period of cool weather. 



Treating seed grain to prevent smut, H. O. Jacobsox et al. (Rpt. Wisconsin 

 Agr. Expt. Assoc, 1904, pp. 62-66). — The results of treating oats with formaldehyde 

 solutions for the prevention of smut are shown by the experience of a number of 

 experimenters in different parts of the State. The directions given in Wisconsin 

 Station Bulletin 98 (E. S. R., 14, p. 978) were followed in all essential details, and 

 all the investigators report a greatly lessened amount of smut and greater yields from 

 treated seed when comparisons were made with small areas grown from untreated 

 seed. 



Black scab of potatoes (Bd. Agr. and Fisheries [London], Leaflet 105, pp. 4, 

 figs. 2). — A brief popular account is given of the black scab of potatoes (CEdomyces 

 leproides), which was first reported in England in the autumn of 1900, having prob- 

 ably been brought to that country with potatoes imported from the Continent. 



This disease, which has been previously described (E. S. R., 14, p. 1085), is char- 

 acterized by the abnormal growth of the tissues about the infected portions of the 

 tuber. The fungus seems to stimulate a rapid growth, resulting in the formation of 

 large, irregular-shaped outgrowths of a blackish color. When potatoes are planted 

 in soil containing the fungus the young sprouts are often attacked and their further 



