THE FLORIST’S JOURNAL. 
of the solar rays, and becomes suspended during the night, or 
when light is withheld; the green colour in leaves is dependent 
on the influence of light, and becomes intense in proportion to 
the degree of exposure to it, within certain limits, which vary 
according to the natural condition of the plants ; in total and 
long continued darkness leaves lose the green colour altogether, 
and become blanched and etiolated. 
The food taken up by the rootlets is gradually conveyed up¬ 
wards through the stem to the leaves, and there becomes de¬ 
composed and assimilated ; probably some alteration takes place 
during its passage through the stem, such as parting with a 
portion of its water, and fixing carbon among the tissue: 
certainly when it reaches the leaves, it is by no means in the 
condition in which it entered the roots, but becomes altered in 
its nature and specific gravity, by taking up what soluble matter 
it meets with in its progress. The changes produced by the ex¬ 
posure of the vegetable fluid in the leaves are principally the 
decomposition of carbonic acid, the abstraction of superfluous 
water by perspiration, and the assimilation of the various remain¬ 
ing matters. Light, and the atmospheric dryness which gener¬ 
ally results from its presence, are believed to be the causes which 
produce these several actions: light is, however, believed to be 
the remote, rather than the direct cause of perspiration, which 
is induced by the dryness produced by means of the heating and 
rarification of the atmosphere when solar light is applied; this 
is apparently illustrated by the fact that plants or flowers when 
exposed to the dry air of a sitting room, though imperfectly 
illuminated, are found to perspire so much more than when in 
the open air, and exposed to direct light, that in such situations 
it is next to impossible to keep many kinds alive : light is, how¬ 
ever, to all appearance the exclusive cause of the decomposition 
of carbonic acid. 
( To be continued .} 
LIST OF NEW PLANTS. 
Vaccinace^e. — Decandria Monogynia. 
Gaylussacia Pseudo- Vaccinium. The genus Gaylussacia, so named after 
M. Gay Lussac, the eminent French chemist and philosopher, differs from 
Vaccinium in the same way as Arctostaphylos from Arbutus — it has but a 
