10 INTRODUCTION. 



appear successive generations of plants, animals, and 

 men. 



We have felt, for many years, interested in the plant- 

 world, that beautiful and ever-variegated carpet with 

 which Nature has overspread the earth, and which is ever 

 changing its character as the seasons roll on. We have 

 also printed several elementary works on Botany, and 

 this time have chosen for our subject, a Tree ; because it 

 is a picture of the whole of Nature, and of the way in 

 which Nature works. 



It is quite evident that each part of a tree, whether it be 

 leaf-scale, or leaf, sepal or petal, has its place assigned 

 and task allotted in the construction of its organism; 

 and that there is a system of mutual dependency and 

 subordination which pervades all the parts of the tree 

 from the cell upwards. Now this variety, and at the 

 same time unity of organic action, so apparent in all the 

 life-phenomena of a tree, and in all the mutations of its 

 form is exceedingly instructive, for it throws light not only 

 on the natural laws which govern society, but on the whole 

 of organized Nature. 



Nature is a mechanism whose parts are intimately as- 

 sociated with each other. The forest leaf, for example, 

 has infinite connections not only with the tree which it 

 helps to build, but with the atmosphere which it oxyge- 

 nates, and with the raindrop which it absorbs and decom- 

 poses. And it is the same with every insect, moss, and 

 mountain floweret. Each has its place assigned in the 

 organism of the universe, and its allotted labors to per- 

 form. All take their part in effecting those grand 

 changes now taking place in nature ; and which are un- 

 doubtedly conducted on a plan devised by infinite intelli- 

 gence and wisdom, and therefore perfect in all its parts, 

 harmonious in all its arrangements. 



In like manner that part of Nature called civilized so- 

 ciety, notwithstanding all the evils with which it is neces- 

 sarily accompanied, is equally a mechanism, and governed 

 by natural law. It is my design in this work to try to 



