FLOWER-GARDENING. 155 



302. For the maintenance of a plant in health, it is indis- 

 pensable that the supply of fluid by the roots should be con- 

 tinual and uninterrupted. 



303. If anything causes perspiration to take place faster 

 than it can be counteracted by the absorption of fluid from 

 the earth, plants will be dried up and perish. 



304. Such causes are, destruction of spongioles, an insuffi- 

 cient quantity of fluid in the soil, an exposure of the spongioles 

 to occasional dryness, and a dry atmosphere. 



305. The most ready means of counteracting the evil conse- 

 quences of an imperfect action of the roots is by preventing 

 or diminishing evaporation. 



306. This is to be effected by rendering the atmosphere 

 extremely humid. 



307. Thus, in curvilinear iron hot-houses, in which the 

 atmosphere becomes so dry, in consequence of the heat, that 

 plants perish, it is necessary that the air should be rendered 

 extremely humid, by throwing water upon the pavement, or 

 by introducing steam. 



308. And in transplantation in dry weather, evergreens, or 

 plants in leaf, often die, because the spongioles are destroyed, 

 or so far injured in the operation as to be unable to act, while 

 the leaves never cease to perspire. 



309. The greater certainty of transplanting plants that have 

 been growing in pots is, from this latter circumstance, intel- 

 ligible. 



310. While the utility of putting cuttings or newly trans- 

 planted seedlings into a shady, damp atmosphere is explained 

 by the necessity of hindering evaporation 



XIIL CUTTINGS. 



311. When a separate portion of a plant is caused to pro- 

 duce new roots and branches, and to increase an individual, it 

 is a Cutting. 



