F. T. Brooks and M. A. Bailky 213 



containing a dilute solution of the dye, placed at a higher level. The 

 exposed portions of roots were enclosed with slates which were readily 

 removable if the roots required attention. At first, absorption of the 

 solutions was rapid, and when it slowed down, the severed ends of the 

 roots were pared, thus allowing absorption again to become vigorous. 

 Dilute solutions of the following dyes were used for this purpose; Congo 

 Red, Gentian Violet, Eosin, Methyl Violet and Methylene Blue. It was 

 not expected that the last-named would prove toxic to the fungus as it 

 is often used in dilute solution for inlra-vitam staining, but, being a 

 very clear stain, one thought it had the best chance of showing, by 

 staining the wood, whether such dyes were carried to the extremities 

 of the trees. The exact strength of these dyes in the transpiration 

 current cannot be given for obvious reasons, but it was considerably 

 less than 1 in 2000, as the solutions were made up at a strength of 1 in 

 2000 or 1 in 10,000. The results were as follows: 



(1) Eosin. Of four treated trees, two recovered although some of 

 the young leaves withered in one of these. A third tree showed partial 

 recovery but some of the leaves were killed. The remaining tree showed 

 no improvement. 



(2) Methyl Violet. One tree recovered but two others showed no 

 improvement. None of the leaves were killed. 



(.3) Congo Red. The only tree treated with this became healthy. 

 None of the leaves were killed. 



(4) Gentian Violet. As for Congo Red. 



(5) Methylene Blue. One tree recovered and one remained silvered. 

 None of the leaves were adversely affected by this dye. 



(6) Control. One tree in which distilled water was absorbed in the 

 same way did not recover. 



In the trees which absorbed these dyes, the xylem of the leaf petioles, 

 especially the lower ones, became stained after a time, methylene blue 

 being most evident, although it could not be detected in the uppermost 

 leaves of the trees. The recoveries in these experiments were more 

 numerous than have ever been observed by us to occur naturally, and 

 it is likely that some at any rate were due to these dyes acting toxically 

 on the fungus without seriously affecting the host. At present, these 

 results are only of scientific interest, and until treatment of this kind 

 has been applied on a larger scale, much importance cannot be assigned 

 to it. From the practical point of view nothing can be done at present 

 along these lines as the methods here used are too troublesome and too 

 costly. If, however, certain of these dyes could be obtained at a cheap 



