ON TIIE INFLUENCE OF SOLAR RADIATION ON PLANTS. 381 
the red light continued to grow healthily, some being 6 inches high on the 
loth; under the yellow and obscured yellow, they also grow healthily; under 
the obscured colourless, the stalks were found on the 22nd no longer capable 
of supporting themselves. The stalks in the dark were at the same time 
erert, and 10 inches in length. On the 26th, the seeds under the colourless 
glass were found to have made scarcely any advance since the 12th. Under 
the blue, one had grown tall and healthy, but the rest were very small. Under 
the red, the plants were growing healthily as on the 12th, but some of them 
had attained the height of 9 inches, and bore three or four secondary 
branches. Those under the yellow had grown, but did not appear healthy. 
Under the obscured colourless glass, the plants had grown since the 12th 
about as much as might have been expected from the time, but they were very 
weak. Under the obscured yellow glass there were two very similar to, anil 
nearly as large as, those under the obscured colourless. 8ix others were ot 
the same character, but much smaller; the roots were very short. The plants 
in the dark had also grown since the 12th. 
On June 5th the experiments were discontinued. The longest pea-plant 
under the colourless glass was then only 1*75 inch in length ; the secondary 
rootlets were remarkably short and thick. The plants under the blue ap¬ 
peared the most healthy ; those under the yellow, whether in full *'8 , 
"bscured, showed considerable inclination to send out lateral branches. 1 ie 
■terns of the plants in the dark were white, the leaflets were canary-yellow; 
liioM' had grown in partial obscurity were also much etiolated. One 
i P eas under the obscured yellow had produced a triple stem, and so 
tad one of those under the obscured colourless glass, as drawn in fig- 7- 
I he average length of the roots ami stalks of those peas which lmd germi- 
^ted under the different solar influences is given in the annexed table ; 
Colourless 
Blue 
Red 
Yellow 
Obscured colourless 
^ured yellow 
for cirii» lant8 i Were rem oved from the bricks and allowed to dry in the air 
had tatr, hours - T »» e following table shows the increase of weight 
£? lo “rless, 
Blu e 
Red 
Yellow 
gfa Earless 
tSS?* yellow ... 
Original weight 
of 12 peas. 
No. of plants 
which had 
germinated. 
Weight. 
33 grs. 
10 
54 grs. 
34-5 
12 
73 
30 „ 
11 
47 „ 
34 „ 
11 
72 
10 
83 
315 „ 
10 
85 „ ; 
31-5 ,, 
12 
150 „ 
Average in¬ 
crease of 
* Very various. 
