84 FAMILIAR LESSOiTS m BOTANY. 



power Ave call chemical affinity. Perhaps I should explain 

 to you the meaning of the word assimilation. 



220. It is a term used to express that process by which 

 different substances are converted into a common substance 

 suitable to the organism of the individual. Tlius food 

 assimilated by a plant becomes a part of the plant ; just 

 as the food you eat is assimilated or converted into the 

 material that makes blood, which replaces the wasted 

 tissues of your body. You now understand a little of the 

 difference between organic and inorganic chemistry, and 

 how the assimilation of food is performed by what we term 

 organic chemical action,t\i-dt is, it is accomplished by living 

 organs, the spongioles, as before explained, having the 

 power of converting inorganic substances, such as lime, 

 potash, iron, magnesia, ammonia, etc., into liquids, com- 

 bining them with the organic elements, oxygen, hydrogen, 

 carbon, and nitrogen, and assimilating the whole into food 

 necessary for the growth and perfection of the plant. 



221. If you are curious to know how much inorganic 

 matter is taken up by a plant, sweep your hearth clean, 

 and barn upon it a log of oak or a branch of ash, or simply 

 a bunch of grass : the organic substances will escape in the 

 form of smoke, vapor, and invisible gases into the open air, 

 while the inorganic earthy substances will remain upon 

 the hearth in the form of asljes. 



222. If you burn rushes or reeds, you will probably find 

 quite a quantity of small shining particles in the ashes; 

 this is silica. These little roots, you think, must possess 

 astonishing power to be able to convert silica into a liquid, 

 carrying it up, and covering the whole stem with it. AVhen 

 you have studied chemistry, you will learn that silica is an 

 acid, and thus combines with the alkalies, soda and potash, 



220. What is the meaning of assimilation ? How is this performed ? 



221. How can jou form some idea of the quantity of inorsranic substances in 

 a plant? What do you find in the ashes? What has become of the gases and 

 vapors ? 



222. What of silica? Kaphides? Where found? 



