INFLUENCE OF SOLAR RAYS ON THE GROWTH OF PLANTS. 23 
grown under actinic influence. Comparative experiments were several times 
made for the purpose of testing this point. 
Coloured solutions «'ere employed, and their results compared with similar 
plants grown under a glass trough filled with very clear water. TJie plants 
employed were the cress, ten-week stocks, aud Venus’s looking-glass. An 
equal weight of the plants was taken from each compartment, and they were 
dried at the temperature of boiling water with great care. The following 
table exhibits the results 
White 
Medium. 
Bed 
Medium. 
Yellow 
^{cdiun1. 
1 Blue 
Medium. 
Percent, 
Admitting of Luminous rays 97 
„ „ Heat do. 75 
„ „ Actinic do. 93 
Per cent. 
56 
84- 
29 
Fcr cent. 
90 
82 
20 
I’er cent. 
51 
60 
94 
Plants gjown. 
Cress (Lepidium sat 
ist Experiment.. 
2nd Experiment-. 
8rd Experiment.. 
Wood. Water. 
g». 
tvum). 
8’2 91*8 
8‘1 yi'9 
8-4 91-6 
Wood- Water 
ITS. 
8-0 92-0 
8-2 91*8 
7*9 92*1 
. Wood. Wafer 
gr*. gn. 
8*1 9JO 
8*3 91*7 
8*4 ei-6 
Wood. Water. 
p*. ft*. 
7*2 92*8 
70 930 
7*6 93*4 
Ten-week stocks (M 
Ist Experiment. . 
2nd Experiment . 
3rd Experiment.. 
atAiola incfina). 
22-0 78-0 
22-7 77*3 
21-9 78'1 
21'5 78*5 
21*7 78*3 
21*4 78*6 
22*2 77-8 
23*0 770 
22*5 77*5 
20*1. 790 
2J0 79*0 
19*6 80-4 
Venus’s looking glass 
ist Experiment.. 
2nd Experiment.. 
3rd Experiment.. 
( Campanula spec 
12'1 87-9 
12'6 87-4 
12-5 87*5 
xlum). 
11-7 88-3 
11*9 88*1 
12'0 880 
120 880 
12*0 880 
12*3 87*7 1 
10*4 89-G 
11.0 890 
10*5 89-3 
Plants growing in tlie shade In like manner contain more water than those 
growing in full sunshine, hence we cannot infer that unylJtirig rnuru than the 
deprivation of light influences the condition of tlie plants in these experi- 
moitts.^ I have ascertained that (mite as great a dllferenco exists in the water 
found in plants growing in artificial shade, and plants of the same dais grow¬ 
ing unslielteitid, iimler iho ordinary conditions of sunshine. It is therefore 
evident that all those experiments which have been made on tbo increase 
ot grass crops by littering the fields with boughs of trees aud the like, arc 
liable to the error alluded to ; and it is very questionable if the increased 
product of nil acre is not principally due to water, rather than to any car¬ 
bonaceous iiroduct, consequently the increase of the nutritive property is not 
in the ratio of the increase of weight, 
lly continuing however tlie experiment for a longer time under the influ¬ 
ences already described, we do learn that the actinic rmliations exert a power 
on the plant, which, although I have previously descrilicd it, I shall particu¬ 
larly call attention to in this plaee. 
It fretjuently Inippcns, when the media employed cut off a large quantity 
of light and admit thn aclinic principle freclv, that no foniiation of leaves 
takes place after the development of the plumule or first leaf-bud; the young 
stem instead of soliditiying remains soft, and, without increasing in diameter, 
