CHAPTER VII. 

 TYPES AND KINDS OF STEMS. 



67. Kinds of plants with reference to the length of their 

 life. There are three kinds of plants as regards the normal 

 duration of their life, annuals, biennials, and perennials. An 

 annual is a plant which makes its entire growth in one year or 

 season, from the germination of the seed to maturity, when new 

 seed is ripened and the plant dies. Some may accomplish this 

 in a few weeks, others require the entire season from early spring 

 to late autumn. There are many examples of annuals among 

 our common plants, as the corn, buckwheat, oats, morning glory, 

 sunflower, bean, pea, etc. A biennial is a plant which starts 

 from the seed one season and lives over to the season of the 

 second year before the ripening of its seed and death. In many 

 of these there is strong root and leaf development the first year 

 with very little stem, while the second year the stem develop- 

 ment is more prominent, the flowers and seed are formed, and 

 the plant dies. Examples are the carrot, turnip, beet, cabbage. 

 The evening primrose is sometimes a biennial. Winter wheat is 

 usually a biennial. When sown in the autumn or later summer 

 it forms strong "stools" by producing numerous branches near 

 the ground. When sown in the spring it becomes an annual, 

 grows more quickly into the long stems, and stools but little. 

 For this reason spring wheat is generally used for spring sowing. 

 Those plants which are sometimes annual, sometimes biennial, 

 are often called transition forms. Perennials are plants which 

 normally live several or many years. Examples are found in 

 most of the grasses, the golden-rod, wild aster, and all shrubs 

 and trees. Some plants have a perennial root-stock and an 

 annual aerial shoot, as in the mandrake, jack-in-the-pulpit, 

 wake-robin, etc. 



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