INTRODUCTION 



Plants exercise, in common with animals, the two princi- 

 pal functions of organic life — nutrition and reproduction. All 

 the organs of the most complex, as well as of the most 

 simple plants, are developed for the purpose of carrying on 

 one or the other of these two functions. 



The tissues which constitute the suhstance of both animals 

 and plants are formed from cells, and exhibit a most re- 

 markable accordance in their vital phenomena. In both, 

 peculiar secretions are carried on, which are restricted to cer- 

 tain parts of the organism ; whilst as life advances to the period 

 of its close, the walls of the fully developed cells become 

 thickened by the internal deposition of matter in layers. 

 Ossification in animals exactly corresponds to lignification in 

 plants. 



Plants as well as animals reproduce themselves. Flower- 

 bearing plants when they arrive at an adult state develope male 

 and female organs, termed stamens and pistils. These mu- 

 tually operate in the formation of an embryo or seed, which 

 contains within its folds, in a rudimentary condition, all the 

 organs of the fully developed plant. These embryos are 

 formed in a particular organ termed an ovule, and are de- 

 veloped in consequence of imbibing the fecundating matter of 

 certain cells termed pollen. Thus, from the vital actions of 



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