DAMPING-OFF IN FOREST NURSERIES. 27 



sites frequently, if not usually, do part of their work before the seed- 

 lings appear above the soil. Furthermore, any treatment at all effect- 

 ive against the disease is almost certain to hurt the seedlings if applied 

 after the seed starts to sprout. 



Both the acid and copper-sulphate treatments which have been 

 found useful in pine seed beds are of very doubtful value for most 

 hosts other than conifers, as the angiosperms on which observations 

 haA^e so far been made are too easily injured by the disinfectants. 

 The weeds in the nurseries have been injured or entirely kept from 

 appearing by treatments which caused no injury to the pines. 



CAUSAL FUNGI. 



CORTICIUM VAGUM. 



Occurrence and parasitism. — In a recent publication (68) Corti- 

 ciiain vagum B. and C. (C vagum solani Burt, Hypochnus solani 

 Pril. et Del. ? the common damping-off Rhizoctonia) has been reported 

 on a number of conifers. Inoculation, reisolation, and reinoculation 

 on pine have established its, parisitism on this host beyond a reason- 

 able doubt, though in these inoculations, as in most, if not all, the 

 work which has been done with the fungus on angiospermous hosts, 

 the cultures employed have been from plantings of diseased tissue 

 instead of from single spores. The inoculation experiments have 

 confirmed the field observations indicating that this fungus is fully 

 as able to cause loss by destroying germinating seed below the soil 

 surface as to cause damping-off of the better known type after the 

 seedlings appear above the soil surface. 



An extensive list of angiosperms on which the fungus has been 

 reported is given by Peltier (98). Cross-inoculations between the 

 pines (68), on the one hand, and potato (40) and sugar beet (38) 

 have shown the same strains to be parasitic on both conifers and 

 angiosperms and established the physiological as well as the morpho- 

 logical identity of the fungus attacking pines with the common 

 Corticium vagum. Now that Duggar (34) has offered strong, 

 though not yet entirely conclusive, evidence of the identity of C. 

 vagum with the European " vermehrungspilz " (the Moniliopsis 

 aderholdil of Ruhland; 115) it is to be presumed that it is 

 a cause of damping-off of conifers in Europe as well as in Amer- 

 ica, though no reports of it on conifers have been so far en- 

 countered in European literature. The Rhizoctonia reported by 

 Somerville (132) on Pinus sylvestris and the Rhizoctonia strobi de- 

 scribed by Scholz (121) as killing young Pinus strobus were both 

 on trees more than 4 years old, so that they had no relation to damp- 

 ing-off. Furthermore, the first of these was apparently the old 

 Rhizoctonia violacea, now known as R. crocorum (R. medacaginis) , 

 a fungus entirely distinct from Corticium vagum, probably belong- 



