Functions of Vegetables . 207 
Duration of plants.— M.axiy plants, as soon as they 
have ripened their seeds, which is accomplished by 
some in one season, by others in two, cease to vege- 
tate ; and hence such plants have been denominated 
annuals and biennials, — terms expressive of their dura- 
tion for one or two years ; but other plants live for a 
great length of time, and continue to produce seeds and 
fruit for many successive seasons ; and hence such 
plants have been called perennials. This diversity of 
duration exhibits a wonderful and endless variety among 
the vegetable tribes. The humble annual springs up, 
displays its leaves, and flowers, and forms perfect seeds ; 
and thus, within the short period of a few months, pas- 
ses through the whole progress of its existence ; while 
the stately oak rears its lofty head, and continues to 
be the glory and pride of the forest for hundreds of 
years. 
THE END. 
Edinburgh .-—Printed by C. Stewart. 
