OPEN LETTERS. 
THE ACTION OF FUNGICIDES. 
In Dr. CLARK’S* paper, in a recent number of the BoraNicaL GAZETTE 
no attempt was made, as the author states, to discuss the literature of the 
subject; but Rumm? has written a paper that has such evident bearing @ 
the subject that it should have received attention. The latter reached the : 
following conclusion, based on experimental evidence closely resembling that 
adduced by Clark as indicating the solvent action on copper hydroxid ¢ 
secretions or excretions from the cells: ‘Die Thatsachen, die uns Calcium . 
und Kupferhydroxydmischungen ergeben haben, erklaren sich leicht, wenn 
man annimmt, dass von Beginn der Einwirkung des Kupferhydroxyds nate 
Spuren dieses Stoffes, welche durch aus den Algen austretende Saures : 
gelést werden, wenigstens bis in die Wandsysteme der Algen vordringen 
den Tod der letzteren bewirken.” Rumm, however, failed to obtain 
Same résults with Puccinia spores. It thus appears that the only. difference 
_ between the explanation offered by Rumm and by Clark for the same 
_homenon is that the former postulates an acid solvent excretion : 
cell, while the latter has shown that saline or other organic | 
= produce the same effects. — 
Clark also failed to notice a short preliminary eile ye 
‘Clic {cnie F.: On the toxic sia poe a some copper 
se cial reference to Bordeaux mixture. Bor. GAZ. 33: 26-48. se : 
_ Ro, C.: Zur Kenntniss der Wirkaag der Bordeau} ' es igs 
oO . longata und die Uredosporen von Puccinia 
age 1:81-156. 1897. A preliminary announcemen 
Ber. Deutsch. Bot. Gesells. 13: 189-192. 1895, and another ¢ 
ments in Jahresh. Vereins vaterl. Naturk. Wiirttemberg 547: 
Bain, SAMUEL ie The injury of — to =~ ie 
4: 231, 222. es au tee tes 
244 
