periments in which older spore-soil mixtures were used on seed- 

 lings with plumules as much as 2 to 2 yd cm. long. It is evident 

 .hn , -Km.. |v 1 !!<•. ((dim ;-s may he infected. 



A series of experiments was also carried out to determine the 

 effect of temperature. Relatively high infections were ohtained at 

 both 20 and 25 ° C. There was a falling off at 30 and 35 , but 

 , ..'ii ' 1 the I; itei 1 mperatm 1 eon dd< 1 ihl< 11 ml) r of srnutte 1 

 plants occurred. The amount, of infection, however, at the dif- 

 ferent temperatures, varied somewhat depending upon the moisture 

 content of the sand or soil and also upon whether the .seedlings 

 were germinated in sand or in soil. 



Forest Pathology 



By Arthur Harmount Graves 



Chestnut Bark Disease Investigations 

 This work was a continuation of that described in my report 



of last year, Hie problem being to determine the cause of the 



greater resistance of the root of (he American Chestnut (Castanet; 

 dentata) as compared with the stem, to the bark disea.se caused 

 by the fungus Endothia parasitica CMurrill) Anderson. The 

 laboratory workoMhi experiment: was carried on In /MC- Hester 

 M. Rusk, and the considerable amount of progress that has been 

 1 1 d> in the wa 11 nil 1 hi largel o her a 1 tan c 



Although it had been assumed hypothetically that the greater 

 content of tannic acid or tannin compounds in the root tissues 

 was responsible foi ill ii grca.tei resista.no to tin fimgou jTouth 

 it was believed po ibi tba.1 mho -in in might b dm to tin 

 comparative lack of air (for it is well known that the fungus in 

 question is an aerobe and therefore needs a good supply of air 

 tor its best development) or to some other factor of the environ- 

 ment of roots, which differs so markedly from that of the stems. 



To get information on this point, i.e., the cause of the greater 

 disease resistance in the roots, three series of inoculations were 

 m I on 1 1 b( 01111 11 1 I nihil n on 1 Own m hi < 11 on 

 an equal number of roots, and trunks or shoots of the same tree. 

 As noted in my last, report, m each, series, after inoculation, the 

 roots were left in a different environment, as follow.-: 



