90 
Adams .— The Effect on Certain Plants of 
The total number of flowers produced in each of the three pots 
exposed to light was sixteen, twenty-two, and twenty, while in the darkened 
pots the numbers were twenty-four, fifteen, and thirteen. 
Experiments with Coolwort (Tiarella cor difolia , L.) in Greenhouse. 
The time of planting and the dates and duration of covering were 
exactly the same as for Liver-leaf. 
The first flower in the three pots exposed to light opened on 25 March 
1922, 29 March 1922, and 2 April 1922, respectively. In the darkened 
pots the corresponding dates were 27 March 1922, 29 March 1922, and 
1 April 1922. 
The total number of flowering scapes in the pots exposed to light was 
fourteen, seventeen, and twenty-one respectively, while in the darkened pots 
the numbers were eighteen, seventeen, and twenty. 
Discussion of Results. 
From the above experiments the following conclusions may be drawn : 
1. The plants exposed longest to the action of light (a) attained the 
greatest weight, (b) attained the greatest average height, ( c ) commenced to 
flower earlier than those which were darkened for a number of hours 
each day. 
2. The above results were not so marked in the case of Soy Bean and 
Tomato. 
3. In latitude 45-!°, where the experiments were carried out, the other 
plants were able to make use of the prolonged daily period of light during 
the summer months with beneficial results. 
Some further comment on these results seems desirable in view of the 
conflicting conclusions arrived at by the other investigators whose views 
were briefly summarized above. Apparently some restatement of the action 
of light on plants is necessary. 
1 a. As light of a certain intensity is necessary for photosynthesis, it 
necessarily follows that, if other conditions remain the same, the plants 
exposed longest to light will attain the greatest weight, and this was con¬ 
firmed by the experiments. 
1 b. As growth in length normally takes place as the result of cell- 
division and cell-elongation at or near the tip of the stem, and as organic 
material is required for such cell-division, it necessarily follows that plants 
provided with a larger supply of such material as the result of prolonged 
photosynthesis are in a better position for making increased growth than 
those not so well supplied. ""Hence plants with a longer period of illumination 
should attain a greater height than those illuminated for a shorter time (other 
conditions remaining the same), which again is borne out by the experiments. 
A better understanding of the situation will be arrived at if attention 
