Page:An introduction to physiological and systematical botany (1st edition).djvu/173



, 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 vascular, sometimes very succulent, and its upper and under 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 elegance of their forms. Their many œconomical uses to mankind, and the importance they hold in the scale of