pec.9, igis Seedliiig Diseascs of ConijeYS 531 



Typical mycelium of Corticiwn vagum is easily demonstrated in the 

 tissues of recently killed pine seedlings, and in the soil adjacent to them, 

 and is obtained in culture by planting in solidified prune-agar plates 

 small soil masses, or recently killed seedlings either with or without pre- 

 liminary washing in mercuric-chlorid solution. Growth on the plates 

 is very rapid, and transfers from the edges of the resulting colony give a 

 large percentage of apparently pure cultures. A distinguishing charac- 

 ter of the hyphae, helpful in conjunction with the typical basal constric- 

 tions and septa, but less commonly mentioned, is the lack of tapering 

 in young branches. Young hyphae are nearly as large as older ones, 

 with thick truncated tips, very unlike the fine tapering tips of some of 

 the other soil fungi whose large hyphae with basally constricted branches 

 might otherwise be confused with young hyphae of C. vagum. 



The coniferous hosts from whose damped-off seedlings Corticium vagum 

 has been isolated are western yellow pine^ and jack pine from Nebraska, 

 red pine (P. resinosa) from Minnesota and Michigan, Engelmann spruce 

 from California and District of Columbia, and Douglas fir (Pseudotsuga 

 taxifolia) from Colorado. Cultures from all of these hosts, with the ex- 

 ception of Douglas fir, have proved parasitic on pine seedlings. The 

 single strain isolated from Douglas fir proved weakly if at all parasitic; 

 so man}' infections have been observed in seedlings of this fir that it is 

 believed some of them have been caused by parasitic strains. The fun- 

 gus was also seen in the tissues of, or in cultures from, damped-ofif seed- 

 lings of Scotch pine (Pimis sylvestris), Corsican pine, Austrian pine 

 (Pinus austriaca), and Norway spruce (Picea excelsa) without attempt- 

 ing to isolate it. With the previously reported findings of the fungus 

 in damped-off white pine (6), yew {Taxus cuspidata; i), and T. cana- 

 densis,'^ the number of coniferous hosts on which C. vagum apparently 

 causes damping-off in nature is raised to 12, and Vv411 probably be much 

 further increased when other conifers are studied. 



Rhizoctonia has also been found associated with needle-killing of 

 white pine (2) and Douglas fir (14) in seedlings more than i year old. 



INOCULATIONS ON AUTOCLAVED SOIL 



Inoculations by the standard method described on page 526 were 

 made with strains of Corticium vagum on conifers in the autumn of 1909, 

 and repeated in later years. Inoculations with agar cultures broadcast 

 at one side of the pot were made on jack pine in two experiments and 

 on both red and western yellow pines in two other experiments, germi- 

 nation being reduced in the inoculated pots, and damping-off appearing, 

 while the controls, with the exception of the red pine in the last experi- 



1 All of the -western yellow pine mentioned in this paper was from seed collected in South Dakota, Colo- 

 rado, or New Mexico, and is therefore the small-seeded fonn of Pinus panderosa Laws (P. scoptilorum Lem- 

 mon). 



' The report of this latter species as a host for Corlicium vaytim is attributed to Clinton by Peltier {21, p. 

 304), though it does not seem to be mentioned by Clinton in (/). 



