CHAP. IV. FUNCTION OP NUTRITION. 239 



this term to animals, but are as well qualified to perform 

 all their functions with vigour and precision after they 

 have existed for many years as when they were young. 

 The causes why such plants perish are not merely those 

 common accidents which result from the influence of 

 the weather, the ravages of animals, and the like ex- 

 ternal accidents, but likewise the continually increasing 

 difficulty they meet with in procuring sufficient nutri- 

 ment. The increasing length of their branches affords 

 greater hold to the wind, and renders them proportion- 

 ably more liable to be broken off and rottenness to be 

 introduced in consequence. But in speaking of the dura- 

 tion of life in plants, we ought to have some definite 

 notion of what we mean by a vegetable individual. 



(236.) Individuality of elementary Organs. Some 

 persons consider every vesicle and other elementary 

 organ of which plants are composed, to possess a dis- 

 tinct and separate existence of its own ; and therefore 

 they look upon every specimen as an aggregate of ve- 

 getable individuals, closely packed together and con- 

 stituting a compound individual. The main facts upon 

 which this singular hypothesis reposes are the follow- 

 ing. There are certain plants among the lowest tribes 

 which consist of only one or at most of very few distinct 

 vesicles, which indicates the possibility of a single de 

 tached vesicle existing as a separate individual. It 

 may be observed however that these plants are among 

 some of the most minute objects of organised matter, 

 and that we know very little of their actual history 

 and scarcely any thing of their physiology. Another 

 argument in favour of the individuality of each vesicle 

 is deduced from a belief that the cellular tissue in every 

 part of the vegetable structure is capable of producing 

 buds or gems, each of which is able to exist separate 

 from the plant on which it was developed, and by 

 proper treatment to become an individual plant similar 

 to its parent. M. Turpin has recorded a very in- 

 teresting and remarkable instance of this description, 

 where a leaf of an Ornithogalum after it had been 



