OEGANS OF GROWTH. 



15 



terms to define the various forms of their peculiar stems, 

 but which cannot be specially entered upon in this work. 



Every separate vegetable growth constitutes a plant, 

 and consists of two special parts — viz., root and stem ; 

 the latter bearing leaves and flowers. In describing 

 a plant we speak of the root, stem, leaf, floiver, fruit, 

 and seed, each of which varies in form and size, accord- 

 ing to the nature of different plants, and it is a question 

 whether we should commence with the germination of 

 the seed, and trace it through all its stages to the per- 

 fect plant, or with the perfect plant, and end by show- 

 ing how the seed is formed, and the changes it undergoes 

 in coming into life. I adopt the latter, and shall treat 

 the whole subject under four different heads — viz., 

 Organs of groivth, Organs of reproduction, Anatomical 

 structure and Vitality, and Classification. 



I. OEGANS OF GROWTH. 

 Roots. 



Roots are that part of a plant by which it is attached 

 to the earth, or bodies on its surface ; sometimes under 

 or floating in water, or suspended in the air ; in all cases 

 increasing in length downwards, and spreading in all 

 directions. They, in conjunction with the leaves, absorb 

 from the earth and air the elements for sustaining the 

 life and forming the numerous substances of plants 

 which chemistry reveals. As might be expected, roots 

 present great variety of form and structure, it some- 

 times being difficult to determine between root and stem. 

 As a general rule, the greater number increase in length 

 by a continuous extension of fibrous points, according 

 •to age thickening backwards, and in large trees becoming 

 woody like the stem. 



