Dec 1922] 
RUTH EFFECT OF BORDEAUX MIXTURE 
539 
motor to the tables by a belt. The motor was located on a separate stand 
to reduce vibration. The period of rotation of the tables was six and one 
half minutes. 
The steam heat of the greenhouse was under thermostatic control, 
maintained at twenty degrees C. The humidity of the air was controlled 
by flooding the broad trenches under the slatted walks and benches each 
morning. At this time the flats were watered. On cloudy days the tables 
were artificially illuminated by stage flood lights, each of which was provided 
with a looo-watt nitrogen-filled tungsten lamp. The distance from the 
lamps to the tables was five feet. The effectiveness of this additional 
illumination as an aid to the normal growth of the plants (Lubimenko, 
1905) is indicated by the prevention of unusual elongation of the stem on 
such days. The results obtained by this artificial lighting may be illustrated 
by the following : December 13, 15, and 16 were very cloudy. On December 
13, the cotyledons of the young plants were just appearing above the soil 
of two flats. One of these was artificially illuminated by means of a flood 
light; the other, similarly located, received daylight only. The length 
of the stem to the primordial lea.ves of the former averaged 9 cm. on 
December 16 (individual measurements, 10, 9, 13, 10, 9, 9, 6, 6, 6, 
12, 9, 6, 11,9, and 9 cm.), while the stems of the latter averaged 15 cm. 
(individual measurements, 16, 16, 13, 16, 15, 14, and 16). (C/. Johnston, 
1917.) 
As soon as the primordial leaves had unfolded the plants were thinned 
out. From twelve to twenty-four plants of uniform appearance and growth, 
and as evenly spaced as possible, were left in each flat. In the experiments 
on the effect of spraying with Bordeaux mixture, the plants in one half of 
each flat were sprayed ; in the experiments on the relation of the chlorophyll 
content to the rapidity of growth of the primordial leaves, disbudding, by 
which the increased rate of growth of the primordial leaves was secured, 
was carried out on alternate plants. In the experiments on the effect of 
age, care was taken to maintain an equal spacing as plants were removed 
during the progress of the experiment. 
The results recorded are based upon data secured through the use of 
the primordial leaves only. No selection of plants or leaves was made at 
harvesting. The leaves were measured and weighed in the fresh condition 
and immediately dried. The areas were determined by drawing the outline 
of the leaves on weighed letter-size sheets of Hammermill Bond paper, and 
weighing the enclosed portion of the sheet. The paper was found to be 
remarkably uniform in weight; nevertheless, each sheet was weighed 
separately. The leaves were dried in a rapid current of air at a temperature 
of from forty-five to fifty degrees C. About an hour was required for 
average-sized leaves. During drying, the leaves were protected from sun- 
light. As soon as the leaves were crisp, each lot was stored in a small tin 
box until its chlorophyll content was determined. 
