38 THE TREES OF AMERICA. 



to other changes than those of mere form. The cell-wall is usually thickened 

 by a deposit between the two walls. This deposit takes place often irregularly, 

 varying in quantity and arrangement ; and if we add to this that lime, silex, &c., 

 are frequently deposited in the cell-walls, we shall understand what produces 

 the almost countless number of differences which exists in the texture of 

 different plants. 



The multiplication of cells, which constitutes usually the growth, of plants, takes 

 place in the following manner. The nutrient matter within the parent cell forms 

 secondary cells, which increase in size while the original or mother cell dissolves 

 and disappears. This process goes on so rapidly in some cases that it is said that 

 in a certain species of mushroom twenty thousand new cells are formed everj"^ 

 minute. The different development of cells, as we have said, produces the different 

 tissues of vegetables. Thus the production of what are called bast cells in the 

 bark of many plants gives us substances of which cordage and various kinds of 

 cloth are made. Such are hemp, flax, New Zealand flax, &c. Another develop- 

 ment of cells produces cork, which is the bark of a species of oak ; and still 

 another, wood itself The colors of plants (with the exception of green, 

 which is found to depend upon colored granules which adhere to the inside of 

 the wall of the cell) depend upon the coloi-ed fluids which are found in the cells. 



Albumen, gum, sugar, citric and malic acids, &c., are found in solution in the 

 cells ; the various vegetable oils are also found there. Another important prod- 

 uct of vegetables, starch, is found packed away in cells ; and in wheat and rye 

 the starch cells occupy the centre of the graiQ, whUe the external cells are filled 

 with gluten. This substance, gluten, is much more nutritious than starch. 

 Hence bread which is made of carefully bolted flour is not as good as that in 

 which what is generally supposed to be a poorer article is used. We have thus 

 glanced at some of the facts which the science of botany reveals to the student. 

 If we have failed to make ourselves clear to our readers, the fault is ours ; it does 

 not, we are sure, exist in the subject itself, which, as it is now taught, may be 

 understood by every one, and should, we are fully convinced, be a leading study 

 in all our schools. The objects of our investigation are every where about us. 

 They enter into every department of life ; and shall we be content to be entirely 

 ignorant of that which it so much concerns us to know 1 



