SECT. II. DISEASES, 505 



SECTION III. 



Natural Decay. 



IN the preceding section I have stated the chief Inducing 

 of the diseases to which plants are liable, whether 

 from external injuries, or from internal derange- 

 ment. But although a plant should not suffer from 

 the influence of accidental injury, or from disease, 

 still there will come a time when its several organs 

 will begin to experience the approaches of a na- 

 tural decline insensibly stealing upon it, and at last 

 inducing death. For in the vegetable as well as 

 in the animal kingdom there is a term or limit set, 

 beyond which the individual cannot pass, though 

 the duration of vegetable existence is very different 

 in different species. 



Some plants are annuals and last for one season Whether 



, . i i i r i . . in the case 



only, springing up suddenly from seed, attaining O f annuals, 

 rapidly to maturity, producing and again sowing 

 their seeds, and afterwards immediately perishing. 

 Such is the character of the various species of 

 Corn, as exemplified in Oats, Wheat, and Barley. 

 Some plants continue to live for a period of two 

 years, and are therefore called biennials, springing 

 up the first year from seed, and producing root and 

 leaves, but no fruit ; and in the second year pro- 

 ducing both flower and fruit, as exemplified in the 

 Carrot, Parsnip* and Caraway. Other plants are 

 perennials, that is, lasting for many years ; of 



