DISEASES OF PLANTS. 643 



It is staled that tliis disease is associated witli species of Fusariuni in 

 soutliern, and of Verticilliuiu in nortlieru, regions. Tlie primary infection takes 

 place from the soil, which, it is thought, may retain the fungus in an active 

 condition for at least live j-ears. Tuhers from shoots not attacked on diseased 

 plants will be sound, while those from infected shoots may be more or less per- 

 meated by the mycelium or may be simply weakened by its presence in the 

 vascular system of the stolon. From an infected seed tuber the mycelium may 

 (though apparently it seldom does) grow into the forming shoots (.secondary 

 infection), or the .seed tuber may give rise to descendants which are simply 

 wealvened as an after-result of the disea.se. Resistance as regards varieties 

 differs greatly, but no coini)letely iunnune varieties are mentioned. 



Control measures reconunended include su.s])ension of potato culture for at 

 least five years on fields which have shown leaf roll ; careful selection of seed, 

 with particular reference to climate and soil; suitable fertilization of the soil to 

 increase vigor in the crop; and careful elimination of plants showing leaf roll 

 (luring growth. 



A bibliograi)hy of contributions for 191'i is added. 



Occurrence of silver scurf of potatoe-s in the Salt Lake Valley, Utah, P. J. 

 O'Gara {ScU'itce, n. ser., Jfl {HU'j), Xo. lO'tl, pp. 131, 13:i).—The author calls 

 attention to the occurrence of silver scurf {BpondijlocJadium. alrovirens) on 

 jiotatoes in the Salt Lake Valley, Utah. From the investigation of the source 

 from which the seed tubers were purchased, it is believed, that this disease is 

 widespread among the iutermoimtain States, particularly in Utah and Idaho. 



An endophytic endodermal fungus in Solanuni tuberosum, E. M. Wilcox, 

 (i. K. K. Link, and Florence A. McCormick (Abs. in Sciowe, n. ser., /fl {1915), 

 No. 10 is, p. 171). — A preliminary account is given of investigations on an 

 endophytic fungus found in .S'. tuherosum. This fungus, it is said, may be found 

 throughout the whole plant, but is confaied to the endodermis. In the usual 

 vegetative propagation of the potato it proceeds from the tuber throughout the 

 shoots to the daughter tubers. The possible relation of this fungus to tuberiza- 

 tion is discussed. 



[Diseases of sugar cane on the island of St. Croix, 1913], L. Smith (Rpt. 

 Agr. Expt. fita. St. Croix, 1912-13, pp. ^5, Ji6). — Marasniiu.'i sacchari is said to 

 cause considerable damage to sugar cane all over the island. Fructifications 

 have been reported from one plantation. 



The chief remedies recommended include planting tops from laud known to 

 have been free fi'om the disease for 8 or 10 years, the employment of Bordeaux 

 mixture for soaking the cane tops 20 minutes befoi-e planting, and rotation, 

 preferably with cotton followed by legumes or these with corn. 



Red rot of the leaf sheath, which does some damage here, has been identified, 

 it is said, with a fungus disease which is common in Java. 



Effect of dilution upon the infectivity of the virus of the mosaic disease 

 of tobacco, H. A. Allard (U. S. Dept. Agr., Jour. Arjr. Research, 3 (1915), No. 

 Ji, pp. 295-299). — Experiments are reported that were conducted with the idea 

 of determining the effect of dilution ui)on the infective power of the virus of the 

 mosaic disease of tobacco. A quantity of expressed snp from diseased leaves 

 was passed through filter paper and all dilutions accurately determined, and 

 Inoculations immediately made from these to young vigorous tobacco plants 

 growing in a greenhouse. 



It was found that the virus of the mosaic disease, when diluted to 1 part in 

 1,000 of water, is quite as effective in producing infection as the original nndi- 

 luted virus. It was observed that adenualion of the virus was indicated when 

 dilutions of 1 part in 10.(X)0 were made. At greater dilutions infection is not 

 considered likelv to occur, The author claims that the evidence iit hand indi- 



