oe OPEN LETTERS 245 
The writer also made an experiment on peach leaves quite similar to the 
one described by Clark, in order to determine whether the leaf gives off any 
_ Sabstance having a solvent action on copper hydroxid, and obtained results 
Similar to those obtained by Clark. But these data do not fer se show the 
_ Solution of copper hydroxid by leaves in general, because of the presence of 
_ am in the sinuses of the teeth of the leaf in question, apparently secreted by 
= the marginal glands. This gum remains, or is freshly secreted during most 
: _ ofthe functional life of the leaf, and must evidently be taken into account in 
_ drawing conclusions from the experiment as made by Clark. There can be 
__ litle doubt, however, that soluble substances escaping from leaves into water 
. on their surfaces will influence the solvent action of this liquid on copper 
_ bydroxid, De Saussure found that washing leaves with distilled water | 
o removes a considerable proportion of the alkaline salts contained in them, 
and Gandichau d/and Sachs found that drops of water standing on leaves 
son acquire an alkaline reaction towards litmus. 
: It appears that Barth 4 was first to propose the theory of the action of 
fungicides on foliage which was stated by Clark. Droop and Wortmann$ 
Said to have disproved Barth’s theory, but the writer has not yet had 
aeve8s to their publications. 
In conclusion, the statement may be permitted that the writer does not 
underrate the importance of Dr. Clark’s paper as a contribution to our 
eof the fungicidal action of the Bordeaux mixture.—SAMUEL M. - 
Ver sit “ Tennessee, Knoxville. — 
REJOINDER. oe 
regard to the foregoing criticism of the treatment of the literature me 
iper, | call attention again to the fact, which Professor Bain izes, 
_ by Was made “to review the literature of the subject." 
oe prelithinary paper, | may add that my paper was. 
the hands of the publishers some weeks before. his ee 
se I may also point out that his paper was snot ct 
. lem as to how the Bordeaux mixture effects its mission as sa 
the chief object of my investigation of Bordeaux mixture; and — 
injurious effect. frequently observed on the leaves of — 
| a discussed incidentally on page 44, I simply b 
3 tors which seemed to me to be of i 
Rg 
mportance in this con- 
ri . 269. 1895. $2Zeits Pllanzenkrankh: 10: 165 
- Gaz, 33 26. 1902. 
