DAMPING-OFF IN FOREST NURSERIES. 7 



tirely on mechanical puncturing for its progress from cell to cell. 

 Hartig (61, p. 147-150) shows a fungus which he does not name, but 

 which is evidently a species of Fusarium, dissolving the young un- 

 cuticularized epidermis of pine seedlings; but he states that it can 

 not so dissolve older epidermis. The increased protective value of 

 the epidermis of older plants can only in part explain the immunity 

 most of them develop against serious attack by damping-off organ- 

 isms, as lesions already started or which may later develop from the 

 infection of young roots are unable to extend into the older parts 

 of the plants. 



It may be mentioned here that the writer in a very preliminary 

 test found strains of Corticium vagum and Fusarium moniliforme 

 Sheldon which had been proved able to cause damping-off of pines 

 also apparently able to destroy filter paper in inorganic salt solu- 

 tion, while Pythium debaryanum seemed not so able. Ruhland 

 (116), on the other hand, found the strain of the " vermehrungspilz " 

 (Corticium vagum) which he tested to be very weak in cellulose- 

 destroying ability as compared with Botrytis cinerea. 



DAMPING-OFF OF CONIFERS. 



HISTORICAL. 



While the losses from damping-off in seed beds of dicotyledonous 

 tree species are occasionally serious and in the case of beech in 

 Europe have required considerable study, they have been so far 

 overshadowed in this country by the losses in coniferous seed beds 

 that practically all the attention thus far, both as to etiology and 

 measures of prevention, has been devoted to the disease in conifers. 



The literature on the damping-off of conifers is considerable. 

 A large part of it, because of the extensive early development of 

 plant pathology and forest planting in Germany, has been writ- 

 ten by Germans. A large portion of the German articles on it 

 was either by foresters or by botanists in the day when most patho- 

 logical work was of the reconnaissance type. Therefore, while the 

 work of one of the best known of the parasites on coniferous seed- 

 lings was noticed in Europe as early as the eighteenth century (21, 

 p. 252-253) most of the European data available are observational. 

 The only fungi which were at all definitely connected with the dis- 

 ease on conifers seem to have been Fusarium (Fusoma spp.) and 

 Phytophthora fagi (P. omnivora De Bary in part). The damping- 

 off Rhizoctonia was described in Germany in 1858 and Pythium de- 

 baryanum in 1874; the fact that neither of these, important in conif- 

 erous seed beds in both the eastern and western United States, has 

 ever been reported from conifers in Europe is perhaps the best evi- 



