It is very difficult to make plants grow in rooms. They must
necessarily be deficient in the three important auxiliaries to
vegetable life, light, air, and moisture; the latter of which cannot
be maintained in apartments that are daily occupied. In large towns,
plants cannot thrive even in the open air, as the minute particles of
soot, which are constantly floating about, settle upon their leaves,
and choke up their pores. The gases produced by the combustion of
coal, &c., are also injurious to plants. Sulphurous acid, which
abounds in the atmosphere of London, turns the leaves yellow; and the
want of evaporation and absorption by the leaves prevents the proper
elaboration of the sap, and makes the trees stunted and unproductive.
_Ibid._
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