Herbs, Shrubs, and Trees 



95 



germinate ; roots and shoots develop ; and by midsummer or 

 autumn, flowers and fruits are produced and new seeds, which 

 contain the beginning of another generation 

 of plants, are formed. Then the plants die. 

 The period from seed germination to seed pro- 

 duction is called the life period. If it is com- 

 pleted within a single growing season, the plant 

 is called an annual (Latin : annus, year). Corn, 

 lettuce, radishes, beans, pumpkins, morning- 

 glories, and ragweeds are familiar annual plants. 

 Biennials. During the first season some 

 plants develop only leaves and roots and a very 

 short stem. The root is usually large and accu- 

 mulates a considerable amount of food. In the 

 second season growth is re- . 



newed, and there is developed 

 an upright stem with leaves, 

 flowers, fruits, and seeds. 

 These plants which pass a 

 winter season during their 

 vegetative development, and 

 whose Hfe period includes two 

 different growing seasons, are 

 called biennials (Latin : hien- 

 nium, space of two years). 



Fig. 57. Moth mullein, a biennial: first 

 season rosettes (in foreground) and 

 mature plant. 



The seeds of some common 



weeds, Hke the shepherd's purse, evening primrose, and wild 

 lettuce, germinate in August or September, and a little rosette 

 of leaves is formed close to the ground. Food accumulates in 

 the root until winter comes. The following spring the plants 

 make rapid growth, and by midsummer they have blossomed, 

 produced seed, and died. In spite of the fact that their whole 



