168 CUTTINGS. 



301. The consequence of such copious persphation is the 

 separation and solidification of the carbonised matter that is 

 produced for the peculiar secretions of a species. 



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 any thing 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- 



M07. Thus, in curvilinear iron hot-houses, in whicri 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 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 

 intelligible 



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. 



XIII. 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. 



312. Cuttings are of two sorts,— cuttings properly so called, 

 and eyes. ^319.) 



313. A cutting consists of an internodium, or a part of one, 

 with its nodus (59.) and leaf-bud. 



314. When the internodium is plunged in the earth it at- 

 tracts fluid from the soil, and nourishes the bud until it can 

 feed itself. 



315. The bud, feeding at first upon the matter in the inter- 

 nodium, gradually elongates upwards into a branch, and sends 

 organised matter downwards, which becomes root?. 



316. As soon as it has established a communication with the 

 soil, it becomes a new individual, exactly like that from which 

 it was taken. 



