196 TEXTBOOK OF BOTANY 



is used in the building of bicycle frames, and in many kinds 

 of machinery. 



The largest grasses with hollow stems are the bamboos, 

 which are inhabitants for the most part of tropical and sub- 

 tropical countries, and some of which reach a height of 120 

 feet and a diameter of eight to twelve inches. Bamboo stems 

 are best known to us by the fishpoles that are made from 

 them. They also supply material for buildings, ropes, mats, 

 and kitchen utensils, and for a great variety of other uses. 

 The grasses are by no means the only plants with hollow 

 stems ; very many annual plants have them. But as a fam- 

 ily, the grasses have carried this principle of stem construction 

 farther than any other group. Some plants, of which the 

 sunflower is one, have the central part of their stems filled 

 with a soft pith. This, so far as strength is concerned, 

 amounts to much the same thing as having the stem hollow. 



216. Trailing Stems. — As we have seen, a plant with an 

 erect stem has the great advantage that its foliage leaves are 

 carried up into the air, where they receive an abundance of 

 light. There are localities, however, which are not suited to 

 plants with erect stems. Such are the sides and tops of cliffs 

 and of rocky hills, where the soil is too thin to allow of the 

 growth of long roots, and where such plants as do grow are 

 exposed to strong winds. Some plants with erect stems — 

 the red cedar, for example, and some shrubs and herbs — 

 do grow in such locations ; but they are likely to be small 

 and stunted and are usually few in number. In such situa- 

 tions we find other plants — such as the creeping juniper — 

 whose stems creep or trail along the surface of the ground. 

 Trailing plants are not so much affected by winds as are up- 

 right plants ; for this reason they do not need the support 

 of long roots that penetrate deeply into the soil ; and since, 

 in locations like those described, they are not shaded by 

 taller plants, their leaves receive the Hght that they need. 

 In bogs, too, and in very sandy places, such as beaches, where 



