180 THE POPULAR SCIENCE MONTHLY. 



envelope ; but liquid and gaseous foods can be easily absorbed. Al- 

 though the most perfect microscopes have never made any holes visible 

 in the cell-envelope, there is not the slightest doubt that this envelope is 

 porous, like a fungus, but that the pores are infinitely finer. Therefore, 

 we may understand that, when a cell is placed in a fluid, the envelop 

 absorbs it to fullness, and conveys to the inner protoplasmic body as 

 much as it requires ; and, inversely, certain parts of the cell-juices, 

 which the living protoplasmic body does not need for itself, are tran- 

 spired through the pores of the envelope and become applicable to the 

 use of other cells ; and the same may take place with air and gases. 



The old naturalists believed that all bodies were composed of four 

 elements fire, water, air, and earth. Modern physics and chemistry 

 have divested these elements of their high importance ; but they are 

 still full of meaning to the life of plants. Earth, air, and water are 

 the food of plants ; fire, or rather light and heat, are the forces that 

 set agoing the play of life in the cells. The most important food of 

 plants is contained in the mineral solutions which the water, penetrat- 

 ing the soil, extracts from it, and in the oxygen and carbonic acid 

 which they derive from the air. 



Water, earth salts, and the gases the raw materials which the 

 plants suck up are changed within the cells into starch and sugar, 

 gum and woody fiber., albumen and wax, oil and resin, into powerful 

 medicines and deadly poisons. The simplest plant possesses an art 

 which the most skillful chemist has not been able to learn from it. It 

 is true that the chemist can artificially prepare in his laboratory many 

 of the substances which the plant-cell likewise produces ; he can con- 

 vert the starch of the potato into the sugar that gives the wine-grape 

 its sweetness ; this, again, he can transform into the fruit-acids which, 

 in connection with the sugar, give the berries their fresh and agreeable 

 taste ; he can even produce the flavor of the fruits from the fusel-oil 

 which he obtains by the fermentation of the sugar. He can make the 

 oil of bitter almonds from benzoic and formic acids ; he can, with as 

 good art, imitate the pungent taste of the pepper, and the biting one 

 of the mustard-seed, and the narcotic poison which only the night- 

 shade has hitherto prepared for the healing of sore eyes. He can 

 produce from the sap of firs the crystal-needles of the vanilla, for 

 which a Mexican orchid has heretofore been obliged to give up its 

 pods ; from the distillation of wood he obtains a smoky fluid, from 

 which he procures salicylic acid, for the production of which the flowers 

 of the meadow-sweet or the bark-tissues of the willow were formerly 

 required ; and from this he makes also the ink-coloring gallic acid, 

 which formerly only a little wasp knew how to draw out by its sting 

 from the cells of the oak, and the aroma of the wood-ruff. He has 

 made the work of the cells in the madder-root superfluous, for he has 

 fabricated its costly dyes, along with a hundred other splendid pig- 

 ments, out of tar-oil and stone-coal ; and is now on the point of taking 



