Dec. 9, 1918 Seedling Diseases of Conifers 549 



occurrence, especially on damped-off seedlings under moist chamber 

 conditions, makes a test of its parasitism desirable. 



The common large Mucor sp. is another fungus frequently found in 

 agar cultures from damped-off pine seedlings. Two strains, one appar- 

 ently pure and the other of somewhat doubtful purity, have been tested 

 in inoculation on jack pine in autoclaved soil. In experiment 31 (Table 

 II shows results of other fungi in this experiment) there was distinctly 

 less damping -off in the 10 pots inoculated with cultures of Mucor sp. 

 than in the 25 control pots. In the experiments on sand treated with 

 acid and lime, the two Mucor cultures gave slig'ht indication of para- 

 sitism on jack pine and still less indication on western yellow pine. In 

 both cases the differences between the inoculated and control plots were 

 well within the limits of accidental variation. It seems probable that 

 strains of Mucor are not of any importance as damping-off parasites and 

 that their frequent occurrence in the cultures from seedlings, as in the 

 case of Trichoderma sp., can be explained by the fact that Mucor sp. is 

 a common soil-inhabiting saprophyte and is able to grow very rapidly 

 in prune agar. 



Penicilliufii sp. of the common green type has occurred more or less 

 frequently in cultures from damped-off seedlings. Mixed cultures con- 

 taining Penicilliurn sp., like the cultures of Mucor sp., apparently caused 

 a decrease rather than an increase in damping-off' in the 10 pots of jack 

 pine to which they v/ere added in experiment 31, and on both jack and 

 western yellow pine in the experiment on soil treated with acid and lime. 



Aspergillus sp. of the common type with black spore heads, obtained 

 from damped-off western yellow pine at Washington, D. C, when in- 

 oculated on five pots of jack pine in experiment 31, apparently caused 

 a decrease rather than an increase in damping-off. In the expteriment 

 on jack and western yellow pine on sand treated with acid and lime, the 

 same was true for this culture, and also in the case of western yellow 

 pine for another strain of Aspergillus taken from damped-off western 

 yellow pine from the Kansas nursery, at which the experiment was con- 

 ducted. This latter culture had no effect on jack pine. Aspergillus 

 sp. has not appeared in culture from seedlings often enough to warrant 

 any suspicion that it is concerned in causing damping-off. 



Phoma betae (Oud.) Fr. (pure culture furnished by Dr. H. A. Edson) 

 in experiment 31, Table II, had no apparent effect on damping-off of 

 pine. The same held true in western yellow pine in the experiment on 

 sand treated with acid and lime, and while a slight decrease in germina- 

 tion and a slight increase in damping-off was noted in the jack pine 

 inoculated with P. betae in this latter experiment, the difference was 

 easily within the limit of accidental variation. The failure of this 

 damping-off parasite of beets to affect pines was to be expected, in view 

 of the specialization of the fungus to beets indicated by the systemic 

 character of the infection it produces on them (8). 



