54 THE STORY OP THE PLANTS. 



Many other plants which live in dry or sandy 

 places, like our common English stone-crops, do 

 not go quite as far as the cactuses, but have 

 thick and fleshy leaves on thick and fleshy stems, 

 to prevent evaporation. As a general rule, in- 

 deed, the drier the situation a plant habitually 

 frequents the fleshier are its leaves, and the 

 greater its tendency to make the stem share in 

 the work of feeding, or even to get rid of foliage 

 altogether. In Australia, however, most of the 

 forest trees, like the eucalyptuses, have got over 

 the same difficulty in a different way ; they arrange 

 their leaves on thv. stem so as to stand vertically 

 to the sun's rays, instead of horizontally, which 

 saves evaporation, and makes the woodland 

 almost entirely shadeless. Many of these Aus- 

 tralian trees, however, have no true leaves, but 

 use in their place flattened green branches. 



Some plants are annuals, and some peren- 

 nials. When annuals have flowered and set 

 their seed they wither and die. But perennials 

 go on for several seasons. Most of them, how- 

 ever, in cold climates at least, shed their leaves 

 on the approach of winter. Bat they do not 

 lose all the valuable material stored up in them. 

 Trees and shrubs withdraw the starchy matter 

 into a special layer of the bark, where it remains 

 safe from the winter frosts, and is used up again 

 in spring in forming the new foliage. This ne\/ 

 foliage is usually provided for in the preceding 

 season. If you look at a tree in late autumn, 

 after the leaves have fallen, you will see that it 

 is covered by little knobs which we know as 



