538 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
and Gies (1903) and Hawkins (1913), may have been involved in the effect 
of additions of other salts. As a result of the work of Boussingault (1878) 
and Bain (1902), there can be little doubt that the relatively insoluble 
calcium salts found in Bordeaux mixture can penetrate the leaf. 
Duggar and Bonus (1918), in a study of the effects of spraying with 
Bordeaux mixture on transpiration, offer as an explanation of its effect on 
this particular process an entirely different hypothesis: The Bordeaux 
mixture, which Duggar and Cooley (1914) regard as a film, acts as a bibulous 
material, taking water directly from the interior of the plant. This ex- 
planation is based on the facts, as observed by them, that xerophytic 
plants show no increased transpiration when sprayed, and that the increase 
occurs, in the case of mesophytes, at night only, at which time the stomata 
are probably suffused with water. 
The manner of action of Bordeaux mixture has remained unsolved. 
The importance of the fact that fhe presence of the precipitate in contact 
with the solution assures a constant supply of dissolved copper salts has 
been brought out by Pickering (1910, pp. 6-9). The low concentration 
can not play the part in Bordeaux mixture that it plays in the case of a 
solution not in contact with the solid phase, where the concentration, as 
Clark (1902) has shown, is important. This fact should overcome some of 
the objections to the penetration theory. 
Materials and Methods 
Plants of Phaseoliis vulgaris (variety Dreer's Extra Early Refugee) were 
used in all the experiments. The seed was obtained in one lot from 
Vaughan's Seed Store, Chicago, Illinois. The plants were grown in the green- 
house, in a uniformly mixed and sifted Urbana brown silt-loam, in flats 
three inches deep, ten and one half inches wide, and twenty-two and one 
half inches long (inside measurements). 
In planting, the slightly moist soil was sifted into the flats and all soil 
within one inch of the top was removed. The beans were laid on this soil 
two inches apart in the row and with four inches between the rows. One 
inch of soil was then added, smoothed off, and evenly compacted. The 
flats were watered and covered until the seedlings appeared above the soil, 
and the latter were then transferred to rotating tables similar to those 
described by Livingston (191 7&, p. 149). 
The rotating tables were located in the center of a south room in the 
greenhouse. The tripods were set on widely spaced two-inch boards, 
which were supported on a solid frame made of iron pipes. The nature of 
the foundation and the height of the platforms above the ground (four 
feet) secured a free circulation of air between the flats, and, together with 
the distance from the heating pipes (six feet), guarded against uneven 
heating and uneven relative humidity. Power was transmitted from the 
