THE NATURAL CONDITIONS OF PLANTS. 53 
which is most abundant when they most need it, 
i.e. in the heat of summer. 
The palms have now been enclosed for fifteen 
years, and owing to the confined state of their 
roots, they will continue for very many years 
without outgrowing their narrow bounds. 
Crocuses and Winter Aconites. — Two cases 
were filled with these plants ; the one placed 
outside a window with a southern aspect, where 
there was sufficient light, but no artificial heat ; 
the other in a warm room, where the light was 
very deficient. The plants in the former case 
exhibited a perfectly natural appearance, and the 
flowers were abundant and well-coloured ; whilst 
in the latter, the leaves were very long and pale, 
and not a single flower was produced. 
Crocuses with artificial light. — A case, fitted 
up precisely as the two preceding, was placed on 
my staircase, close to a gas lamp. The plants 
were covered during the day with a thick dark 
cloth, so as effectually to exclude daylight, and 
as soon as the gas was lighted, the cloth was 
removed. The plants were thus exposed from 
five to eight hours daily to the influence of arti- 
ficial light, accompanied by some increased de- 
gree of heat, while the remainder of the twenty- 
four hours was spent in a state of rest. The 
plants grew well, the leaves not so much drawn 
