1164 EXPERIMENT STATION RECORD. 



series of experiments with Altemaria solani to determine whether it has lost its 

 power of developing saprophytically. 



Healthy leaves and leaves infected with Phytophthora infestans were inoculated 

 with conidia of A. solani, and after developing, the spores were gathered and sown 

 on leaves attacked by the late blight. These infections were repeated for six genera- 

 tions, when the conidia were sown on healthy leaves and kept in a damp chamber. 

 The conidia germinated freely, but the mycelium was poorly developed and no spot- 

 ting of the leaves resulted, the mycelium appearing to live almost entirely on the 

 surface of the leaves. 



It appears that through a space of six generations this fungus, which has become 

 parasitic, was so reduced through gradual adaptation as to be converted into an 

 obligate saprophyte. 



Heart rot of beets, mangels, and Swedish, turnips (Jour. Bd. Agr. [Loiidon], 

 12 (1906), No. 10, pp. 596-598, fig. 1). — A description is given of a disease, attributed 

 to the fungus Rphxrella tabifica, which is said to be not uncommon in France, where it 

 causes considerable damage to sugar beets. In England the fungus has recently made 

 its appearance, being particularly destructive to mangels and Swedish turnips. 



The disease rarely appears before the middle of August, and first attacks the stalks 

 of the largest leaves. Its presence is indicated by the wilting of the leaves, such as 

 follows a hot, dry day; during the night the diseased leaves do not recover, but 

 remain lying on the ground, turn yellow, and decay. Later in the season, when the 

 leaf stalks are dead and dry, a second form of fungus fruit appears on the bleached 

 patches, and some time later the mycelium of the fungus passes into the crown of 

 the root, gradually extending downward. Finally the entire root is reduced to a 

 blackish decayed mass. 



The fungus seems to be able to pass the winter in diseased roots left in the field, 

 and where the disease appears, it is recommended that the crop should be harvested 

 immediately and all diseased leaves and roots gathered and burned or deeply buried. 



Yellow varieties of mangels appear to be more susceptible to disease than others, 

 as shown by infection experiments. 



The drop disease of cabbage, J. Ritzema Bos ( Tijdschr. Plantenziekten, 11 (1905), 

 pp. 105-117, pis. 3) . — A description is given of a disease of cabbage said to be due to 

 Phoma oleracea. It has appeared in some of the most important cabbage growing 

 districts of Holland and is proving quite destructive. 



Three fungus diseases of the cultivated ginseng, H. S. Reed (Missouri Sta. 

 Bid. 69, pp. 43-66, figs. 9). — According to the author, ginseng plantations have 

 increased in number and extent so that ginseng now constitutes an important crop 

 in the State. 



The first occurrence of disease on ginseng plants was reported in 1904. At that 

 time the disease seemed to be due to a leaf-spot fungus, and it was thought that 

 spraying with Bordeaux mixture might keep it in check. Later investigations 

 showed that a number of diseases were present and they were not similar to those 

 described from New York (E. S. R., 16, p. 271). On this account the author made 

 a detailed study of the diseases and the fungi causing them. The diseases described 

 are stem anthracnose, leaf anthracnose, and wilt. 



The stem anthracnose is due to the fungus Yermicularia dematium, and it makes its 

 appearance about 30 days after the plants appear above the ground, producing numer- 

 ous black scars on the stems of the plants. The stalks are frequently so badly 

 attacked that they break off before the upper portions become wilted. The direct 

 injury is due to the filaments penetrating the cortical and sclerenchyma layers, dis- 

 integrating them, and later breaking through the epidermis and forming black 

 spore-producing bodies This disease can be readily checked by the use of Bordeaux 

 mixture. 



