144 



General Botany 



Biennials. During the first season some plants develop only 

 leaves and roots and a very short stem. The root is usually large 



and accumulates a considerable 

 amount of food. In the second 

 season growth is renewed, and 

 there is developed an elongated 

 stem with leaves, flowers, fruits, 

 and seeds. These plants which 

 pass a winter season during their 

 vegetative development, and 

 whose life period includes two 

 different growing seasons, are 

 called biennials (Latin : hien- 

 nium, space of two years). The 

 seeds of some common weeds, 

 like the shepherd's purse, even- 

 ing primrose, and wild lettuce, 

 germinate in August or Septem- 

 ber, and a little rosette of leaves 

 is formed close to the ground. 

 Food accumulates in the root 

 until winter comes. The follow- 

 ing spring the plants make rapid 

 growth, and by midsummer they 

 have blossomed, produced seed, 

 and died. In spite of the fact 

 that their whole life is passed 

 within a twelve-month period, 

 these plants are called biennials, 

 because their life period covers 

 parts of two growing seasons. 



The term annual or biennial as 

 applied to plants, therefore, does 

 not imply any definite length of 



Fig. 83. Wild carrot {Daucus carota), 

 showing the plant as a seedling, at the end 

 of the first growing season, and as a ma- 

 ture plant during the second growing year. 

 The life history shown above is typical of 

 biennials, 



