HIBERNATION 125 



biennial is given. Beetroot and Parsnip are other examples. 

 The Radish and the Turnip (see Fig. 26, 2, 3) are also 

 biennials, but the food-material in these is stored mainly 

 in the greatly enlarged hypocotyl. These plants, therefore, 

 tide over one winter by means of their enlarged roots or 

 combined roots and stems, and the following winter only 

 their well-protected seeds remain to perpetuate the race. 

 Just as there are variations in the life-period of annuals, 

 so there are in that of biennials. If we nip off the flowers 

 of biennials the plants continue to vegetate for years, and 

 many so-called biennials, like the Foxglove and Snap- 

 dragon, often continue to grow for several seasons. Again, 

 many plants which are annuals in the plains grow for many 

 years in the mountains. 



Perennials. A large number of our wild plants regularly 

 persist from year to year and may flower each season ; 

 they are called perennials, and in the case of certain 

 trees may live to a great age. The ability to persist, and 

 flower at intervals through several seasons, is termed 

 perennation. In plants with shoots too tender to with- 

 stand the rigours of winter, i. e. herbaceous perennials, we 

 meet with many interesting forms of hibernating organs. 



Underground shoots : rhizomes. In studying a plant like 

 the Stock we receive the impression that the part below 

 ground is mainly root, but it is not easy to decide where 

 the root ends and the shoot begins. Pull up a plant of 

 either the Quick-grass (Wicks), or the Soft-grass, and 

 examine it carefully. What structures do you find ? Is 

 the whole of the underground part root ? By what 

 characteristics will you decide which is root and which is 

 shoot ? Do you find leaves on any of the parts ? If so, 

 what kind of leaves are they ? Can you find buds arising 

 in the axils of any of them ? What do these buds become ? 

 Trace some of them. Are these structures found on some 

 of the underground parts and not on others ? What are 



