186 THE POPULAR SCIENCE MONTHLY. 



constituent of the vegetable body. Our atmosphere is an enormous 

 coal-mine, many miles in thickness, that can not be exhausted in thou- 

 sands of thousands of years. The coal, indeed, is not found pure in 

 the air, any more than the metal in the ore, but is in combination with 

 oxygen as a transparent gas, carbonic acid, and a peculiar art is re- 

 quired to separate it. 



In the mining districts, smelting-houses are erected beside the pits, 

 where the noble metal is extracted from the impure ores. The green 

 cells of the leaves combine the art of the miner with that of the smelt- 

 er, and have the power of extracting the pure carbon from the atmos- 

 phere. In order to perform this work, they must be shone upon by 

 the sun, for the sunlight alone can excite in them the marvelous 

 faculty. Having extracted the carbon, they combine it with water 

 and with the mineral substances that have been drawn from the soil, 

 and prepare from them the living matters out of which the plant itself 

 builds up its cells, and which, taken up into the body of an animal, is 

 transformed by it into flesh and blood. 



As bees do not at once consume all the honey they collect, but lay 

 away a large portion of it in special cells for winter provision, so a por- 

 tion of the cells in the plant are set apart for the storage of capital in 

 anticipation of the necessities of the future. On the approach of winter 

 the leaves discharge the greater part of what they have produced 

 through the conducting vessels, which convey it to a subterranean maga- 

 zine. The cells of the root-stock, the tubers, and the bulbs, protected 

 from the frost by their covering of earth, are filled with starch, albu- 

 men, and other valuable food-material, which will be used again in the 

 coming spring when they will be most needed, for the expansion of the 

 leaves and flower-buds. When we eat a potato, we appropriate to our 

 own nourishment the provision which the careful mother-plant has laid 

 up in its cells during the previous year for the growth of the next 

 spring ; and we do what is substantially the same as when in the fall 

 we rob bees of a part of the honey which they have gathered for the 

 supply of their own state. 



A necessary consequence of the short duration of the life of the 

 single cell is that a part of the plant, the cell- village, in which the life- 

 processes are now active, is generally dead in the next year, and unfit 

 for all work. Therefore the cell-state is subject to a constant mor- 

 tality. The leaves which perform their work in the summer wither 

 and drop off in the fall ; the cells of the root, also, which then drew up 

 the fluids from the soil, and those of the stem, which conducted it up- 

 ward, have at the same time grown old have become woody, as the 

 botanist expresses it. 



The greater part of the plant does not, in fact, survive the first 

 year. Most herbs sprout in the spring, blossom in the summer, ripen 

 their seed in the fall, and perish in the winter. Trees, on the other 

 hand, bushes and shrubs, possess a regular economical administration. 



