THE FLUID COMPONENTS OP PLANTS. 247 



was found to possess all the properties of the ligneous 

 fibre. In the seed lohes a greater quantity ol this 

 woody fibre was fount! than in the proper juice of the 

 plant itself; a fact which accounts lor the rapid growth 

 and increase of parts of the young plant, before the 

 roots are able to take up from the earth the principles 

 of nutriment. The proper juices of plants, both in the 

 seed, and in the perfected plant, contain nourishment 

 already properly adapted for assimilation into the sub- 

 stance of the plant. But this preparation takes place, 

 either during the time, or alter, the sap has been ex- 

 posed to the action of the light and air in the leaf; as 

 no woody fibre is found in the ascending sap, although 

 the principles of it are undoubtedly contained in that 

 fluid. A new chemical combination of these princi- 

 ples takes place ; but how this is effected, or by what 

 means the change is produced, we know not; and it 

 is one of those mysteries of nature from which human 

 ingenuity will never perhaps be able to remove the 

 veil. In the same manner the blood of animals con- 

 tains the components of the muscular fibres already 

 formed; and an assimilation of it is constantly going 

 on, without our being able to perceive it, or even to 

 form the most distant conception cf the manner in 

 which it is performed. 



The elementary principles of the proper juice 

 of plants and of the sap are the same ; but differ 

 in the relative proportions. These elements are car- 

 bon, hydrogen, and oxygen. The same principles, 

 differently modified, form all the secretions and the 

 solid materials of the plant itself. The extrane- 

 ous ingredients which some plants are found to con- 

 tain, as part of their substance, such as the alkaline 

 and neutral salts, metallic oxyds, silex, and other 

 earths, are often probably obtained ready formed in 

 the soil, in a state of division sufficiently minute 



