74 WINDOW GARDENING. 



requisite for window plants ; for it has been shown that, in other circumstances, 

 ventilation may be dispensed with. 



It is well known that by animal respiration, oxygen — the life-sustaining 

 principle of the atmosphere — is abstracted, and replaced by carbonic acid gas, a 

 compound of oxygen and the carbon of the blood. By a beautiful law of 

 adaptation, in which the mutual dependence of the animal and vegetable 

 kingdoms is strikingly displayed, this carbonic acid, which to the animal 

 economy is a deadly poison, is the chief source of the nourishment of plants. Under 

 the influence of the solar rays, this carbonic acid is absorbed by the leaves through 

 their breathing pores or stomata, and then decomposed, the oxygen being exhaled, 

 and the carbon becoming fixed to form the substance of the plant. By this double 

 process, the constituents of the atmosphere are maintained in tbeir normal pro- 

 portions; and so far, therefore, from a supply of fresh air being necessary to 

 preserve the health of plants, they will flourish in structures hermetically 

 sealed, or at least so close that the amount of leakage is very small, as long since 

 shown by Mr. W ar( j f "Well-close Square, London. The absence, however, in 

 these structures of the injurious gases to which we have already referred, is an 

 indispensable condition to their success; and as, in an ordinary apartment, this 

 condition cannot be ensured without a certain degree of ventilation, it follows, that 

 in practice a stagnant atmosphere, however appropriate in pure media, is not 

 desirable for window plants. In admitting fresh air, hoAvever, cold currents must 

 be carefully guarded against, especially in the winter season, when it should bo 

 very sparingly given, and the door of the apartment should invariably be closed, 

 whilst the window remains open. 



The lateral direction of the light necessarily occasions a distorted growth, which 

 is the more exaggerated, in proportion as the plants are kept at a distance from the 

 glass. 



For this, there is no real remedy ; it is a common practice to attempt to 

 obviate the evil, by turning the plants round, a course which so far from improving 

 their appearance, inevitably increases the distortion. A much better course would 

 be to admit upon the window, only dwarf compact specimens, and to preserve 

 them in this form by constant ' stopping.' Hard-wooded plants which have become 

 drawn up and 'leggy,' should be rejected as incurable, a few cuttings of the 

 healthiest shoots being first taken off, when it is thought desirable to preserve a 

 stock of the same plant. 



The evil to which we have just alluded cannot be said to interfere with the 

 health of the plants, so much as with the perfection of their form ; but the absence 

 of suflicient moisture in the air of most apartments, which causes greater exhalation 

 from the leaves than can be compensated by the absorptive functions of the roots, 

 is attended with more serious results. 



