COPPER SPRAYS ON IRISH POTATO TUBERS. 5 
Working with a large number of greenhouse plants, Zucker (52) 
concluded that plants sprayed with Bordeaux have greater resistance 
to etiolation than the unsprayed plants. The sprayed plants also 
showed an increase of chlorophyll and an increased power of assimi- 
lation, and their shoots lived longer. All of the sprayed plants 
transpired more than the unsprayed plants or those sprayed with 
lime alone. 
Harrison (22) found that Bordeaux-sprayed plum, peach, and pear 
leaves were slightly thickened and that a marked development of 
chlorophyll granules occurred in their cells. 
According to Chuard and Porchet (6), copper spray causes a 
slight increase in the sugar content of matured fruits. Injection of 
solutions of copper salts into the tissues of such plants as the grape- 
vine produced more vigorous growth, more intense color, and greater 
persistence of the leaves. ‘The copper seemed to act as a stimulant to 
all the cells of the organism. Other metals, such as cadmium and 
iron, are said to give a similar effect. Injecting small quantities of 
copper salts into the branches of a currant bush caused an acceler- 
ation in the maturation of the fruit identical with that obtained by 
the application of Bordeaux to the leaves. If the quantity of copper 
introduced into the vegetable organism was increased, the toxic action 
of the metal was brought into play. These investigators attribute 
the stimulus, as shown by the earlier maturation of the fruit, to a 
greater activity of all the cells of the organism and not to an excita- 
tion of the chlorophyll functions alone. 
Treboux (49), in 1903, demonstrated the harmful effect of solu- 
tions of copper salts on leaves, measuring the activity of photosyn- 
thesis by a determination of the rate of emission of bubbles of oxygen. 
Kanda (25) undertook to ascertain whether copper had a stimu- 
lating action on plants. He found that very small amounts of copper 
sulphate were toxic to peas grown in distilled water. 
Schander (4/7) believes that the copper in a Bordeaux spray pene- 
trates the leaf to a very small extent, perhaps less than one in a 
hundred million parts, and that the copper there produces changes 
in assimilation and in transpiration. He considers that the shading 
effect of the Bordeaux spray on the leaves is beneficial to the absorp- 
tion of carbon dioxid. 
Ewert (/7) states that in the morning Bordeaux-sprayed potato 
plants contain more starch than the unsprayed plants, not because 
‘they are making more starch, but because they are unable to get rid 
of it as rapidly. The starch is piled-up in the chlorophyll bodies 
as the minute amount of copper absorbed checks the diastase action. 
Bordeaux spraying, shading the plants with cloth, and a combination 
_ of the two procedures diminish the yield of tubers. This author 
demonstrated by its effect on diastase that copper is present in the 
sprayed leaf in minute amount and concludes that the organic life 
of the plant is hindered rather than stimulated by the application 
of Bordeaux sprays. 
Von Schrenk (50), working with cauliflower, also observed that 
See were formed on the leaves owing to the action of copper 
salts. 
Amos (1) studied the effect of Bordeaux mixture on the assimila- 
tion of carbon dioxid by the leaves of plants to determine whether any 
