altering the Daily Period of Light. 
The plants were cut at 
results : 
Exposed pots 
Darkened pots, Ser. i 
n n it 2 
the ground level on 18 July with the following 
Average height 
Tallest 
Total 
of stem. 
plant. 
weight. 
mm. 
mm. 
grm. 
2 95-5 
3 IQ 
77 - 97 ° 
2 55 -° 
283 
63.79° 
294-5 
330 
77.970 
Experiments with Dandelion in Greenhouse , 1921-2. 
Seeds were obtained from plants which had flowered in 1921 and on 
which the seeds were ripe in the month of May. Two pots were sown on 
28 May 1921, and subsequently five plants were left in each pot. One 
of the pots was darkened periodically, a wooden box being used for the 
purpose, while the other pot was exposed to daylight. The period of 
darkening extended from 1 6 June to 30 July and included altogether 
I 57i hours, about two-thirds of the time being sunny. 
On 31 August one flower head in the darkened pot opened, but there 
was none on that exposed to light. The five plants in the latter case were 
larger than those in the darkened pot. No further flowers were produced 
during the year 1921. On 29 March 1922 the first head in the pot exposed 
to light opened, while the first head in the darkened pot did not open until 
3 April. 
The total number of flower heads produced by the five plants in the pot 
exposed to light was twenty-two, while in the darkened pot the total number 
of heads was nine. In the darkened pot both plants and heads were 
smaller than in the case of the pot exposed to light. 
Experiments with Liver-leaf (Hepatica acutiloba , DC.) in Greenhouse. 
In order to test the effect of a shortened period of light on plants which 
grow naturally in the shade of a forest, two species were experimented with, 
namely Liver-leaf ( Hepatic a acutiloba , DC.) and Coolwort ( Tiarella cordifolia , 
L.). It might naturally be expected that too much light in the case of such 
plants would have an injurious effect. 
Six plants of Liver-leaf were dug up from the floor of a wood and 
placed in pots on 20 June 1921. The plants were approximately of the 
same size. After they had become properly established in the pots, three 
were darkened from 4 July to 30 July. The total time of darkening 
amounted to ninety-four and a half hours. The weather during about two- 
thirds of the time of covering was sunny. 
The dates of opening of the first flower in the three pots exposed to 
light were respectively 20 February 1922, 28 February 1922, and 8 March 
1922. 
The corresponding dates in the three darkened pots were 1 March 1922, 
6 March 1922, and 10 March 1922. 
