3 ON THE INFLUENCE OF SOLAR RADIATION ON PLANTS. 241] 
The experiments were started on Nov. 13th. In order to change the air, 
the shades were lifted off for a minute or two about every second night. 
Each plant grew healthily and flowered ; yet some differences were observed 
of a character which might fairly be attributed to the quality of the light. 
First, as to the rootlets. Under the colourless glass they grew abundantly ; 
under the blue glass they also grew abundantly and more rapidly ; under the 
red glass scarcely any rootlets were produced, and what there were never 
attained any considerable length ; while under the yellow glass they were few 
in number, but long. Secondly, as to the leaves and flower-stalk. Under 
the colourless glass they were put forth in process of time and grew healthily. 
No difference was noticeable under the blue; under the red long spreading 
leaves were put forth, that bent towards the light in a very marked manner, 
and the plant had an unhealthy appearance; while under the yellow glass 
short sturdy leaves and flower-stalks were produced. 
As to the flower itself, it began to open at about the same period in each 
instance, namely,— 
Under colourless glass, on Feb. 11th, or after 90 days. 
Under blue “3 » 10th, He 89 ,, 
Under red os 53 8th, ss Si Gs 
Under yellow 5 » 10th, ie 89 ,, 
There was no observable difference in the colour of the four flowers, not- 
withstanding the variety of tint under which they had been formed. The 
flower under the red glass was long and thin. Latterly they all suffered 
for want of room. 
On April 16th all the plants were removed from the water into which their 
rootlets dipped, dried in the air, and weighed. ; 
Primary weight of bulb. Weight of fully developed plant. 
Under colourless glass 1305 grs. 2118 grs. 
Under blue 3 1328 ,, 2026 5; 
Under red 3 1135 ,, 1386 ,, 
Under yellow 3 1299 ,, 1704 ,, 
showing an increase of — 
Under colourless glass, as 1000 : 1623 
Under blue 5 1000 : 1525 
Under red et 1000 : 1221 
Under yellow 9 10,0. 0 Raa ee I 3 
The greatest srowth therefore was in the plant exposed to all the influences 
of the solar ray. 
Cereals were also grown under the various glasses, a comparative experi- 
ment being made under a darkened shade. Access of air was permitted to 
the plants by the glasses being placed upon boards which were perforated 
_ with holes close together, and were raised about one-third of an inch from the 
table. No direct rays of light could enter, especially as the space under the 
_ boards was blocked up on the side nearest the window, and any diffused light 
finding access by the perforations had to pass through several folds of tarla- 
tane of the same colour as the glass shade itself. 
On Sept. 12th three grains of white wheat, sown in garden mould, to which 
a little stable manure was added, were placed under the various glasses. The 
_ wheat began to grow in a few days in each instance, one seed only under the 
red glass proving unproductive. They were watered as occasion required. 
In a week or two the plants under the darkened shades attained a consider- 
(1852. R 

