HYGIENIC CONDITIONS OF GLASSHOUSES 21 
three months Flammarion found that the height in the 
red house was 0:5 metres, in the white house 0-38 metres, 
in the green house 0-1 metres, and in the blue house 
0-035 metres. 
While plants in the red house were the highest they 
were not the heaviest, for the weight of stem and leaves 
in the white house was 8-4 gms., in the red house 4:6 gms., 
in the green house 0-3 gms., and in the blue house 0-15 gms. 
Lettuce plants grown under white glass developed large, 
thick leaves with good heads ; under red glass the leaves 
were drawn, long, and drooping; under green glass 
they made a slight growth; while under blue glass 
practically no growth occurred. Experiments with peas, 
beans, and coleus plants yielded similar results. 
Further experiments were concerned with root develop- 
ment under different glasses, and indicated that the root 
systems were greater under white glass than under red 
glass, while poor root action was exhibited under green 
and blue glass. Similarly, the mechanical tissues showed 
better development in plants under white glass than 
those under red, green, or blue. 
Flammarion showed that the colour of many flowers 
can be changed by growing them under different coloured 
glass. Thus certain blue flowers become pink in a white 
glasshouse and white under red, green, and blue glass. 
Also, if pale blue lilac flowers are placed under a dark 
bell jar they become a clear red-violet. He also showed 
that the normal amount of red pigment in coleus leaves 
is reduced under red glass, and practically disappears 
under green and blue glass. 
These experiments of Flammarion are of practical 
interest to growers of plants under glass as pointing 
to the importance of using glass of consistent purity, 
because the preponderance of any group of light rays 
has an important bearing upon the plant cultivated 
under their influence. 
(c) Glasshouse Construction in Relation to Air Capacity 
and the Ventilation Factor.—Just as the light conditions 
