266 



Mycologia 



It is possible, of course, that the progress of the fungus in 

 these shoots was slower than in older trees. But even if con- 

 siderable allowance is made for this assumption, it seems more 

 than probable that these shoots did not become infected for some 

 time, probably several years, after they started. That Polystic- 

 tus versicolor is capable of living for that length of time even 

 without much growth cannot be doubted, for Bayliss (i, p. 20) 

 has proved that the mycelium of this fungus can retain its vitality 

 in a dried stick for at least four years. Observations at Soldier, 

 Kansas, indicate clearly that Polystictus versicolor is capable 

 of attacking seedlings even younger than these sprouts. Cer- 

 tainly the fungus spreads rapidly enough from the trunk of a 

 tree into its branches ; and it readily attacks and fruits on one- 

 year old sprouts around the base of a living tree. 



It is not entirely clear, therefore, why these coppice shoots were 

 not attacked and killed much earlier; but it seems possible that 

 this temporary " immunity " may be due to the rapid growth of 

 the sprouts. Both Hartig and Sorauer have cited examples of 

 wound parasites which, although capable of causing the decay of 

 woody portions growing at an ordinary rate, are unable to at- 

 tack rapidly growing parts. Hartig (3) states that in the case 

 of an oak attacked by Armillaria mellea, one may readily observe 

 that the parasite has not developed equally, but usually toward 

 one side. According to him, the development is arrested when 

 the fungus comes to a region directly under the influence of a 

 vigorous shoot. 



Sorauer (6, p. 192) discusses the parasitism of Nectria cinna- 

 barina and states that this fungus is apparently unable to attack 

 sound, rapidly growing tissue of the host. This writer has ob- 

 served in the case of small trunks of Acer Negundo attacked by 

 Nectria cinnaharina, that in the spring the progress of the fungus 

 is stopped by the more vigorous growth of the wood. Sorauer 

 further states that in larger trunks where a sound side shoot has 

 developed, the fungus in the main trunk kills the tissue up to the 

 part which is under the influence of the vigorous side shoot and 

 there remains stationary. It seems possible that something like 

 this occurs in the case of diseased catalpa stumps which have 

 given rise to vigorous coppice shoots. That is to say, that the 



