90 BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. 



(14) In an inoculation experiment on the roots of pines L| months 

 old, Corticiwn vagum and Pythium de~baryanum were found able 

 to cause the death of seedlings which had already developed rigid 

 stems and to destroy the younger parts of the roots of seedlings which 

 they were unable to kill. Indications were also obtained of similar 

 but less vigorous action by Fusarium moniliforme and F. ven- 

 tricosum. 



(15) Data are given confirming the general belief that thick sow- 

 ing favors the disease and indicating that soil acidity is, in general, 

 unfavorable. Preliminary data on the relation of temperature and 

 moisture to the disease are also presented. The parasitic activity of 

 Pythium debaryanum in steamed soil was in one extensive test con- 

 siderably decreased, following the inoculation of the soil with various 

 saprophytes; this indicates both that competition of different fungi 

 is a factor to be considered and that the inoculation of treated soil 

 with saprophytes may sometimes prove of value in increasing the 

 efficiency of heat disinfection. It is pointed out that with such a com- 

 plex of parasites capable of producing identical symptoms on a num- 

 ber of different hosts, no relationship between environmental factors 

 and the disease can be expected to hold in all cases. 



