20 THE ELEMENTARY STRUCTURE OF PLANTS. 



internal activity and unceasing change in living bodies; these 

 constantly undergoing decomposition and recomposition, particles 

 which have served their turn being continually thrown out of the 

 system as new ones are brought in. This is true both of plants 

 and animals, but more fully of the latter. The mineral, on the 

 contrary, is in a state of permanent internal repose : whatever 

 changes it undergoes are owing to the action of some extraneous 

 force, not to any inherent power. This holds true even in respect 

 to the chemical combinations which occur in the mineral and in 

 the organic kingdoms. In the former they are stable ; in the lat- 

 ter they are less so in proportion as they are the more under the 

 influence of the vital principle ; as if in the state of unstable equi- 

 librium, a comparatively slight force induces retrograde changes, 

 through which they tend to reassume the permanent mineral state. 

 6. Consequently the duration of living beings is limited. They 

 are developed, they reach maturity, they support themselves for a 

 time, and then perish by death sooner or later. Mineral bodies 

 have no life to lose, and contain no internal principle of destruc- 

 tion. Once formed, they exist until destroyed by some external 

 power ; they lie passive under the control of physical forces. As 

 they were formed irrespective of the existence of a similar body, 

 arid have no self-determining power while they exist, so they have 

 no power to determine the production of like bodies in turn. The 

 organized being perishes, indeed, from inherent causes ; but not 

 until it has produced new individuals like itself, to take its place. 

 The faculty of reproduction is, therefore, an essential character- 

 istic of organized beings. 



13. Individuals, The mass of a mineral body has no necessary 

 limits ; a piece of marble, or even a crystal of calcareous spar, 

 may be mechanically divided into an indefinite number of parts, 

 each one of which exhibits all the properties of the mass. It is 

 only figuratively that we can speak of a mineral individual. Plants 

 and animals, on the contrary, exist only as individuals ; that is, 

 as beings composed of parts, together constituting ah independent 

 whole, which can be divided only by mutilation. Each may have 

 the faculty of self-division, or of making offshoots, which become 

 new and complete individuals. It is in this faculty, indeed, that 

 reproduction consists. The individuality is no less real in those 

 animals of lower grades, and in plants, where successive genera- 

 tions of individuals remain more or less united with the parent, 



