ON THE INFLUENCE OF SOLAR RADIATION ON PLANTS. 375 
February 13. 
February 21. 
March 22. 
Under the 
colourless glass . 
4 inches 
6 inches 
11 inches 
blue „ .. 
6 
8 „ 
14 
red . . 
3 „ 
5 » 
11 ». 
yellow „ . 
2 „ 
3 
8 .. 
obscured colourless glass 
3 „ 
34 „ 
10 „ 
obscured vellow ,, 
3 „ 
34 „ 
12 „ 
f» 
dark glass . 
3 „ 
4 „ 
10 „ 
The flower-stalk very nearly kept pace with the leaves. There was a 
(treater difference in the periods at which the petals opened than in the 
former series of experiments; those under the blue and colourless glasses 
took the lead, and those under the partially obscured glasses were the last. 
They opened for the most part during the last days of February. Under the 
red shade two flowers grew, but they were thin and straggling: the same 
was tin; character of the plant that grew in the dark. There were two flower- 
*talks under the partially obscured colourless glass; they were never deve¬ 
loped, however, but were found at the end of March losing their colour and 
.coining rotten. The experiments wore terminated on March 22nd, except- 
ln 8 die two under the partially obscured glasses, which were allowed to con- 
" nue Wl the 30th. The respective lengths of the flower-stalks were then,— 
Under the colourless glass. 13 inches. 
» blue „ . 13 ,» 
» red „ . 12'5 „ 
» yellow „ . 12 „ 
» obscured colourless glass . 1 » 
m obscured yellow „ 10 i, 
•» dark H 13 » 
hJT hyacinths having been removed from the water in which their roots 
t u . n „. )ee J 1 'totoersed, were suffered to dry in the open air ot the room for 
twenty-four hours, and were then weighed. 
d r tlle colourless glass . 
blue 
red ” |"|”. 
yellow . || HI!”. 
obscured colourless giass 
obscured yellow 
dark glass . 
If ' 
8‘bal weiu|!'i'°/,?' Js f rv ' ri S the actual increase of weight, we compare the ori- 
follo 'ving propVrtS n >Ulb W * th that ot ' the Tully developed plant, we obtain the 
^ nder the colourless glass as. 1000 : 1596. 
” „ . ... 1000 : 1708. 
” r ed „ . 1000 ; 1680. 
” yellow „ . 1000 : 1395. 
” “bscured colourless glass as. 1000 : 1822 . 
obscured Uow . 1000 . !784. 
" dark 1000 : 1579. 
Primary weight 
of bull). 
Fully deve¬ 
loped plant. 
Actual 
increase. 
936 grs. 
862 „ 
856 „ 
1009 „ 
873 „ 
872 „ 
763 „ 
1494 grs. 
14 72 „ 
1 438 „ 
HOG „ 
1591 „ 
155G „ 
1205 „ 
558 grs. 
610 „ 
582 „ 
398 „ 
718 „ 
684 „ 
442 „ 
