1866.] and Botanical Congress. 451 
Professor De Candolle then read his inaugural address. He 
commenced, by showing “the service that horticulture renders, or 
may render, to Botany. The most remarkable experiments of 
physiologists—viz. those of Hales, Duhamel, Knight, Gaertner, 
and M. Naudin—have been made in gardens. Horticulture has 
done much to advance the progress of physiological botany, but it 
has still much to do.” M. De Candolle then suggested the con- 
struction of experimental green-houses and hot-houses, and gave his 
views as to the plan to be adopted in their erection, so as best to 
serve the purpose of the physiologist. “A building such as I 
propose, would allow of light being passed through coloured glasses 
or coloured solutions, and so prove the effect of the different 
visible or invisible rays which enter into the composition of sun- 
light. M. Von Martius placed some plants of Amaranthus tricolor 
for two months under glasses of various colours. Under the 
yellow glass the varied tint of the leaves was preserved. The red 
glass impeded the development of the leaves, and produced at the 
base of the limb, yellow instead of green; in the middle of the 
upper surface, yellow instead of reddish brown; and below, a red 
spot instead of purplish red. With the blue glasses, which 
allowed some green and yellow to pass, that which was red or 
yellow in the leaf had spread so that there remained only a green 
border or edge. Under the nearly pure violet glasses, the foliage 
became almost uniformly green. Now that plants with coloured 
foliage are becoming fashionable, it may interest horticulturists to 
know that by means of coloured glasses, provided they are not 
yellow, they may hope to obtain at least temporary effects as to the 
colouring of variegated foliage.” “ Nothing would be easier than to 
create in the experimental hot-house an atmosphere of carbonic 
acid gas, such as is supposed to have existed in the coal period. 
Then it might be seen to what extent our present vegetation would 
take an excess of carbon from the air, and if its general existence 
were inconvenienced by it. Then might be ascertained what 
tribes of plants could bear this condition, and what other families 
could not have existed, supposing the air had formerly had a very 
large proportion of carbonic acid gas.” “ Horticulture has a com- 
mercial tendency which may be carried too far. A horticulturist, 
who allows himself to be influenced by a scientific spirit, necessarily 
frees himself from over-selfish tendencies.” The above extracts 
