New YorK AGRICULTURAL EXPERIMENT STATION. 263 
covered with a felt of fine hairs. Examined under the micro- 
scope, One sees upon the epidermis of the young apple many 
stomata. In time the hairs and most of the stomata are lost, 
the former dropping off leaving a distinctive scar, while the 
latter split through surface expansion and give rise to a corky 
formation agreeing with the structure, and, I take it, the func- 
tion of the lenticels. The hairs are thin walled and consist of 
a single cell. The walls of the neighboring epidermal cells, 
even at an early age, are thicker and stronger and as the fruits 
develop this difference becomes more marked. So far as the 
Baldwin and Rhode Island Greening are concerned the stomata 
are not to be found in any considerable numbers after the fruits 
are half grown, though a few are present almost up to harvesting 
time. In the young fruits these stomata are very evenly dis- 
tributed over the surface of the apple. 
These plant: hairs and stomata are the parts of the epider- 
mis which seemingly permit the entrance of the toxic ingredient 
of bordeaux mixture. In its first stages bordeaux injury appears 
as tiny black or brown specks. Under the microscope these 
specks are found to consist of a circle of dead cells usually sur- 
rounding a stoma, but sometimes one of the thin celled hairs. 
It may be assumed that the copper salts are dissolved by mois- 
ture or other atmospheric agencies and enter the cells through 
the stomata, and possibly the hairs, and destroy them. Whether 
the young apples secrete through the hairs, or otherwise, a liquid 
which would dissolve the copper salts in small quantities, is 
notknown; it is possible, and it seems very probable, that there 
is such a secretion, in which case injury might arise independ- 
ently of atmospheric agencies. 
Schander®! holds, after investigations of his own and a con- 
sideration of the work of others, some of whom are not in accord 
with his views, that plants do secrete liquids which dissolve the 
copper salts. Clark, as we have seen, page 235, gives the sol- 
vent properties of cell sap on copper hydroxid as a factor in 
bordeaux injury. He says further: “When the dew is on the 
leaf we have two solutions — the dew drop without, and the cell 
sap within — separated by a more or less permeable membrane. 
These conditions must result in the exosmosis of at least some of 
~ aciander (53,.p.. 279). 
* Clark (13, p.:44). 
Biclack (12, pass): 
