20, 6 Mendiola: Weight and Ash Content of Tobacco 643 
mination plates when they were still too small to be transferred 
into the culture medium. In Crop II, therefore, seeds were 
germinated in sand in a seed box. 
Culture—All plants were grown in water cultures; those of 
the first crop in Erlenmeyer flasks of 2,000 cubic centimenters’ 
capacity. The nutrient solution was prepared according to the 
following modified Pfeffer’s formula: 
Gram per 
liter. 
Calcium nitrate 0.4 
Sodium chloride 0.1 
Magnesium sulphate 0.1 
Monopotassium phosphate 0.1 
Ferric phosphate 0.1 
0.1 
Potassium nitrate 
To obtain different environmental conditions that should per- 
mit of different amounts of transpiration, the plants were grown 
in two glass chambers, each of about 432 cubic decimeters’ capa- 
city. One was “humid,” the other, “dry.” In the humid cham- 
ber a pan of water whose surface area was nearly equal to that 
of the bottom of the room was kept throughout the experiment. 
No pan was used in the dry chamber ; instead, there was a small 
electric fan which was allowed to run for a portion of the time 
of experimentation. As the two rooms were kept closed all 
the time except while changing the solution or watering, provision 
was made for some change of air inside. A tube about 7 milli- 
meters in diameter led from each chamber to the outside, where 
they met in a T-tube which was connected with a Richard’s 
suction pump. 
Some idea of the difference in relative humidity and tempera- 
ture in the two culture chambers can be obtained from the 
temperature and Lembrecht polymeter readings which were 
taken at intervals on July 26 and 27 and are recorded in Tables 
2 and 3. 
TABLE 2.—Temperature and humidity readings on July 26, 1917. 
Humid room. Dry room. 
i iE Weather. 
a — Relative Temper Relative |Tempera-| 
humidity.| ture. | humidity.| ture. 
a.m. p.m. | Per cent. °C. Per cent.) °C. 
1 8.00 68 29.0 55 81.0} Bright, sunny. 
Se 12,30 53 | 82.7 4s|  35.1| Do. 
eee 3.00 51 34.0 41 86.4 Do. 
PSOE es 4,00 62 82.3 €2 83.4 | Cloudy. 
rae ee 28.0 70 28.1 | Rainy. 
Ba a ee 6.00 16 ee te 
