PART I. 



ON THE SIMPLE ELEMENTARY ORGANS OF PLANTS. 



1. When the structure of plants is examined, parts of that 

 structure are found to have peculiar functions assigned them ; 

 these parts are called organs, and the structure is said to be 

 organized. The lower tribes of plants possess fewer separate 

 organs, and the functions exercised are more general and less 

 restricted than in the higher tribes of plants in which the 

 organs are more numerous and complicated. The organization 

 of a plant is considered to be complex or simple, highly de- 

 veloped or the contrary, just in proportion to the number of 

 distinct organs of which it is composed, and of separate and 

 peculiar functions exercised by its tissues. 



2. The organization of plants, when examined with the 

 microscope, is seen to consist of a united mass of cells or 

 vesicles, tubes, and fibres. These cells, tubes, and fibres, 

 which in some of the lower forms of vegetation are developed 

 as separate and independent plants, gradually unite together 

 as organization advances in complexity of structure, and con- 

 stitute the substance of the more highly organized plants. 



