44 BOTANICAL GAZETTE [ JANUARY 
3. The host plant has a greater or less power of dissolving 
the Cu(OH), deposited on its leaves. 3 7 
This solution of the copper by the host plant may or may 
not be advantageous in protecting it from attack, as injurious 
Spores may or may not chance to be present at the point where 
solution has taken place. To this factor, however, must be 
attributed the injury frequently observed with certain plants 
(e. g., Japanese plums, peach, etc.) when sprayed with Bordeaux. 
The amount of injury done to a given species will depend on 
the following considerations, provided always that carefully pre 
pared Bordeaux mixture has been used: = 
I. The specific susceptibility of the protoplasm of the plant t 
poisoning by copper. 
2. The solvent properties of the cell sap on copper hydr 
3. The permeability of the epidermis or cuticle? to these 
ae | following spraying, particularly | 
ditions as regards moisture (dew, etc.), providing the condi 
. n f some of the contents of the cells of the 
_ To these might be added, perhaps, climatic conditions wht 
: through modifications of structure, of specific resistance, of © 
| the character of the cell sap, May cause a plant to be more 
___ Fesistant to treatment with Bordeaux mixture, according to 
locality where it is grown. The very injurious influence 
: Bordeaux mixture on blossoms** is to be explained in an ent 
similiar Way. Here the protection of the cells by cutinization 
almost or entirely wanting, and it is very probable that the 
oo DEW. C Sturgis (itep: Coun: 4 
oS tira of Bordeaux mixture on peac = 
~~ amfortunately neni cone eeePtibility which he found in his peach 
eure caneag. overlooked the Prergeed of specific sensitiveness to cop} 
gric. Exper. Sta. 219-254. 1900) | . 
i -ach foliage. 
3 
the 
ge ens Ome ih he stady of the re of leaves the study of the 
thee epidermis has been omitted, It is hardly possible that the : 
ey nen . can be a factor in the case. oe a 
A., and Barney, L. He ae as ok aap sciped blak 
