124 THE VEGETATIVE ORGANS 



fare ? By what means do they tide over the winter ? 

 We know that many animals burrow in the ground beyond 

 the reach of frost and cold, and lie dormant until more 

 favourable conditions return. But do plants hibernate ? 

 and if so, how ? Let us consider a few common species, 

 e. g. Shepherd's Purse, Turnip, Daisy, Lily, Bluebell, 

 Crocus, and Iris, and note how they pass the winter. 



Annuals and ephemerals. The Shepherd's Purse pro- 

 duces a number of seeds in the summer, but when these are 

 shed the whole plant, roots and shoots, dies, and nothing 

 remains but the seeds. In the following spring the seeds 

 germinate, new plants are formed, which produce flowers, 

 fruits, and seeds the same year ; and the plants, as before, 

 die completely in the winter. 



Species which thus complete their life-cycle in one 

 season are called annuals. They hibernate either as seeds 

 or, less frequently, as fruits, and this is a very effective 

 method. Many of our common weeds of roadsides and 

 cornfields behave in this way, e. g. Groundsel, Chickweed, 

 Field Pansy, Charlock, and Hemp Nettles. Some of these, 

 like the Shepherd's Purse, may pass through their life- 

 cycle in a few weeks if conditions are favourable, so that 

 several generations may be produced in a season ; such 

 short-lived ' annuals ' are known as ephemerals, and 

 examples may often be found among the plants of 

 a waste-heap. 



Biennials. The Carrot behaves differently. After the 

 seed has germinated, the plant grows vigorously ; its root 

 enlarges considerably and becomes stored with a reserve 

 of food-materials (see Fig. 26, 1). In this condition it 

 passes the winter. On renewal of growth in the following 

 spring it produces an abundance of flowers, fruits, and seeds, 

 at the expense of the food stored in the root, which is 

 exhausted ; the seeds are shed and then the whole plant 

 dies after two seasons' growth To such plants the name 



