454 PLANTS AND THEIR RELATION TO MAN 



live on from year to year, become larger and stronger with time* 

 and have woody stems. Other plants, like peonies and violets, 

 die down to the ground after they have borne flowers and fruit, 

 and come up afresh the following spring from protected old roots 

 or germinating seeds. Plants which die down to the ground 

 with the approach of winter are called herbaceous plants or 

 herbs, and have succulent stems in place of the woody stem of 

 long-lived plants. Some of our most popular vegetables are 

 the soft succulent stems of herbaceous plants, for example, 

 asparagus and celery. Stems are not always erect and above 

 ground ; sometimes they are under ground and are short and 

 swollen, as in the white potato (Fig. 321). The food made by 

 the leaves of the potato plant is passed down the erect stems 

 above ground to stems under ground, and accumulates there, 

 swelling and bulging them into tubers. You can easily 



convince yourself that 

 the white potato is a 

 swollen underground 

 stem by examining it 

 and noting the tiny 

 buds or eyes which are 

 scattered over it. Be- 

 cause buds never grow 

 regularly on roots the 

 white potato cannot be 

 called a root. It is 

 really a swollen under- 

 ground stem or tuber. 



Woody stems as lum- 

 ber. Woody stems, 

 branches, and trunks 

 are most valuable for 

 FIG. 322. Conifers. the lumber which they 



