84 



It has been observed that plants will lengthen very fast during dark- 

 ness in a high, moist atmosphere, and it has therefore been supposed 

 that a gain in growth is thus secured; but strictly this is not the fact. 

 Any extension of growth made under such conditions is at the expense of 

 that made during the presence of light, as it is only then that those 

 chemical changes are in operation that change the matters absorbed by 

 the roots into the woody fiber and other constituents of plants. Conse- 

 quently the same quantity of material is simply elongated, as in draw- 

 ing out a wire, which may be lengthened without adding anything to 

 its structure. 



Plants grown in a nearly uniform temperature under glass seldom 

 ripen or mature their wood in a thorough manner; the buds are imma- 

 ture and make feeble growth, and the whole plant contracts a delicate 

 habit of constitution, which renders it incapable of withstanding the 

 slightest neglect without injury, thus entailing great care to keep it, 

 even in its sickly condition, and never by any means developing its 

 natural capacities. On the contrary, plants constantly subjected to a 

 suitable lowering of night temperature are more robust, have short- 

 jointed and matured growths, flowers not only expand more fully, but 

 remain longer in perfection, fruits better colored and flavored and more 

 perfect in every respect than those developed in an atmosphere of uni- 

 form heat and moisture. 



With regard to greenhouse plants, it should be remembered that they 

 require no heat during the night further than to exclude frosts. It has 

 been stated and urged as a reason for keeping a higher temperature 

 that it is necessary to do so in order to secure a succession of bloom, 

 but it had been amply proved that by allowing a more liberal heat, say 

 from 70 to 80 during the day, that a more profuse crop of flowers 

 will be gained than in the more equable conditions insisted upon. 



Another injury consequent upon a high night temperature during 

 winter arises from the extraction of moisture from the atmosphere. To 

 maintain an inside temperature of even 50 when the, external is near 

 zero involves a rapid generation of heat, and as the capacity of air for 

 taking moisture increases in proportion to its rise, a great demand is 

 made upon the plants and everything in the house capable of giving 

 up moisture. The quantity of water thus carried off may be seen by 

 the deposition of ice on the inner surface of the glass after a night of 

 severe frost. Ice one-fourth of an inch in thickness is often found 

 under these circumstances, the result of condensation and freezing of 

 the water carried from the contained moisture in the atmosphere and 

 from the surfaces of the plants. The parched and unhealthy aspect 

 of the plants subjected to such treatment is sufficient evidence against 

 the propriety of the practice. The expense of fuel and labor required 

 to maintain this injurious temperature is also an important consider- 

 ation. 



