X INTRODUCTION. 



however humble may be its manifestations of vitality or simple 

 its organic structure. 



And let me suggest that the study of the simple plants ought 

 to take the precedence of those whose organization is more com- 

 plex and intricate, as being the simplest expression of the laws 

 of vegetable life. It is now certain that the growth of plants, 

 and, in fact, of every organic being, is the result of the opera- 

 tion of certain fixed and immutable laws. All who have no- 

 ticed the phenomena of the life of plants must be satisfied 

 that this is the case. Thus, all have a period of life assigned 

 them, more or less limited, during which we see them, as it 

 were, by successive increments, slowly elaborated out of the 

 earth and atmosphere, arrive at the full perfection of their 

 growth and beauty, reproduce themselves, and then die. The 

 period of time during which these phenomena take place varies 

 according to the peculiar structure of each plant. Thus plants, 

 whose structure is very simple, as ferns, mosses, and many of 

 our fiowering-plants, grow, reproduce themselves, and then die, 

 and this all in a single season. In other instances, where the 

 organization is higher, the duration of life is much longer. 

 But the forest-tree, lifting its massive stem for centuries to the 

 light of day, has also an appointed period to its life, as regular 

 as the lowly moss that grows beneath its shade. A few months, 

 however, suffice to perfect the one, and many centuries are re- 

 quired by nature before she can build up the other. Now it 

 is evident that the growth of the humble moss is only a sim- 

 pler expression of that same law which operates in the produc- 

 tion of the forest-tree ; and if we can explain the law of deve- 

 lopment in the one case, we can in the other. 



