DISEASES OF PLANTS. 743 



badly iufected, while those eoniing from trees cut in 15)07 showed little or no 

 disease. TBe author questions whether the funj^us, which is generally consid- 

 ered a wound parasite, is responsible for all the injury, and he believes there is 

 considerable evidence to show that winter injuries contribute very materially 

 to the spread of the disease. 



In continuation of previous investigations on artificial cultures of Phyto])h- 

 thora with special reference to oospores ( K. S. K., 20, p. 11.38), experiments have 

 been carried on with a number of species of I'hytophtliora. In the previous pub- 

 lication reference was made to the possibility of sexual mycelia, but in the pres- 

 ent account, which is based on more than a thousand cultures of potato and 

 Lima" bean mildews, the results seem to throw considerable doubt upon the 

 theory. The life history of the fungi is shown on the different cultures, and 

 the cultural melliods. media, etc.. are described at considerable length. 



Some plant diseases of 1908, L. H. Pammel and Charlotte M. King (lou-n 

 ^ta. liiil. lO.'i. pp. J3Ji-2.j9, fiffs. 11). — Notes are given on smut, downy mildew, and 

 spot disease of millet, powdery mildew of wheat, black blight of wheat and 

 oats, and bean anthracnose and rust. 



The millet smut, which was noticed in the fall of 1908, is caused by the 

 fungus UstUago era inert. The fungus occurs in the smaller spikelets and com- 

 pletely destroys them, leaving only the outer wall of the ovaries. At times it 

 may become so serious as to destroy the crop almost entirely. Investigations 

 seem to show that the disease is transmitted to the seed, and some studies 

 were carried on to determine the effect of formaldehyde and corrosive sul)li- 

 mate solutions on the germination of spores. The stronger solutions of both 

 fungicides completely i)revented the germination of the spores, and it is 

 recommended that seeds should be treated either with formalin or corrosive 

 sublimate before sowing. Investigations have shown that the hot-water treat- 

 ment is also effective, but it does not appear to have any advantage over the 

 formalin treatment. 



The downy mildew of millet (Sclcrospora graminicola) appears to be widely 

 distril)uted and occurs not only on the cultivated millet but also on wild foxtail 

 and other host plants. This fungvis, from the nature of its growth, does not 

 yield to fungicides, and on this account attempts should be made to plant 

 millet in fields where this plant and foxtail grasses have not been grown. 



A spot disease of millet {Piricularia grisea) was reported as seriously 

 affecting the, crop. This disease is readily recognized by the pale green or 

 yellowish ai)peai"ance of the leaves and definite purple or reddish colored spots. 

 These spots usually elongate and the center collapses with the progress of the 

 disease. The fungus has long been known as a troublesome parasite, occurring 

 on a considerable number of grasses. No experiments appear to have been 

 made for the treatment of this disease, but some varieties seem less subject to 

 the fungus than others, and it is recommended that more resistant kinds be 

 cultivated. 



The powdery mildew of wheat {Erysiphe graminis) was unusually prevalent 

 in some of the plats at the station, occurring on certain varieties to an inju- 

 rious extent. This fungus has been reported in different parts of the country, 

 occurring on a large number of grasses, and its development seems to be due 

 to combinations of heat and moisture. On this account grain should not be 

 too thickly sown. I'nacclimated varieties seem particularly susceptible to this 

 trouble, and where the disease is prevalent it is reconnnended that well-accli- 

 mated varieties be selected for sowing. In other investigations (E. S. R., 17, 

 p. 873) it has been suggested that biologic species of W. gramini.-t are present. 

 The authors placed a number of species of grasses iu contact with leaves of 



