178 THE STORY OF THE PLANTS. 



the oak, the ash, the pine, the chestnut, and the 

 maple. 



Once more, some plants produce an under- 

 ground stem, and send up from this fresh annual 

 branches. That is the 'case with hops, with 

 meadow-sweet, and with buttercup, as well as 

 with many of our garden flowers. When a plant 

 becomes perennial, it is a mere question of its 

 own convenience whether it chooses to produce a 

 thick and woody stem, like trees and bushes, or to 

 lay up material in undergound roots, stocks, and 

 branches, like the potato, the dahlia, the lilies, 

 the bulbous buttercup, the crocus, the iris, the 

 Jerusalem artichoke, and the meadow orchis. 



Ordinary people divide most plants into three 

 groups herbs, shrubs, and trees. But I think 

 you will have seen from what I have just said 

 that in every great family of plants different 

 kinds have found it worth while to adopt any one 

 of these forms at will, according to circumstances. 

 Trees, in other words, do not form a natural 

 group by themselves; any family of plant may 

 happen to develop a tree-like species. Thus the 

 herb-like clover and the tall tree-like laburnum are 

 closely related peaflowers. Most of the com- 

 posites are mere herbs or shrubs, but a very few 

 of them in the South Sea Islands have grown into 

 large and much-branched trees. The grasses are 

 mainly herbs ; but some of them, like the bam- 

 boos, have developed tall and tree-like stems, 

 much branched and feathery. 



Take the single family of the roses, for ex- 

 ample, so familiar to most of us ; some of them 

 are mtere annual weeds, like the tiny parsley-piert 

 that occurs as a pest in every garden. Others, 

 again, are perennials with low tufted stems, like the 



