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CHAPTER XV. 



OF LEAVES, THEIR SITUATIONS, INSERTIONS, SURFACES, AND 

 VARIOUS FORMS. 



Folium, the Leaf, is a very general, but not universal, 

 organ of vegetables, of an expanded form, presenting a 

 much greater surface to the atmosphere than all the 

 other parts of the plant together. Its colour is almost 

 universally green, its internal substance pulpy and vas- 

 cular, sometimes very succulent, and its upper and un- 

 der surfaces commonly differ in hue, as well as in kind 

 or degree of roughness. 



Leaves are eminently ornamental to plants from their 

 pleasing colour, and the infinite variety as well as ele- 

 gance of their forms. Their many ccconomical uses to 

 mankind, and the importance they hold in the scale of 

 nature as furnishing food to the brute creation, are sub- 

 jects foreign to our present purpose, and need not here 

 be insisted upon. Their essential importance to the 

 plant which bears them, and the curious functions by 

 which they contribute to its health and increase, will 

 presently be detailed at length. We shall first explain 

 their different situations, insertions, forms, and surfaces, 

 which are of the greatest possible use in systematical 

 botany. 



The leaves- are wanting in many plants, called for 

 that reason plant^e aphylU', as Salicornia, (41) Engl. 

 Bot. t. 415, and 1691, Stapella variegata, Curt. Mag. 



(41) [Samphire or Glassvort.} 



