News and Notes 



43 



lege Agriculture Experiment Station. The resistance of certain 

 plants to the attack of disease-producing fungi has been often 

 observed and discussed. It has been accounted for first by cer- 

 tain structural characters or impervious leaf surfaces and then by 

 the assumption of a peculiar resistant type of cell due to physio- 

 logical and consequently chemical differences zmthin the cell. 

 Now, the first of these explanations was early disproved by the 

 researches of Ward and others while the idea of physiological 

 resistance has not been investigated as much as its importance 

 would seem to make desirable. Dr. Cook attacked this problem 

 with the idea of discovering, if possible, to what extent the sub- 

 stance tannin, of almost universal occurrence among plants, may 

 function in their immunity against fungous diseases. Later it is 

 intended to extend the investigation to include the other cell con- 

 stituents having a possible bearing upon such immunity. 



The methods of study were well planned and carefully carried 

 out. It consisted, briefly, in inoculating different types of culture 

 media, containing varying amounts of tannin, with a large number 

 of parasitic and saprophytic fungi known to produce plant dis- 

 ease. In general it was found that tannin inhibited the growth 

 of the fungi and that this effect was more pronounced in the case 

 of the parasites than with the saprophytes. Small amounts of 

 tannin seemed to have a stimulative action upon growth and fruit- 

 ing but usually from o.i per cent, to 0.4 per cent, tannin had a 

 strong inhibitory effect. It was thought that the acidity of the 

 tannin might account for its observed action upon the fungi but 

 upon experimentation it appeared that even after neutralization 

 with sodium hydroxide the tannic acid radicle still showed its 

 characteristic inhibitions to a large extent. Different amounts of 

 sugars and protein in the media had very little effect in reducing 

 the toxicity of tannin. 



The action of tannin upon the germination of the spores was 

 found to be unfavorable if it were present in anything more than 

 slight amounts. In toxic percentages the time necessary for 

 germination was considerably increased. On the other hand, in 

 smaller amounts tannin acted as a stimulant of germination. 

 Some interesting tests were performed by placing cultures of 

 certain fungi upon very thin cork sheets which had been treated 



