STEMS AND BRANCHES AND THEIR USES 205 



bear small leaves. The large leaves that make most of the 

 plant's carbohydrate food are borne on shorter, more erect 

 branches. Each runner has a terminal bud which, under 

 favorable conditions, can grow into a leafy shoot ; and when 

 the rest of the runner dies, the new shoot with the adven- 

 tive roots that it bears is an independent plant. A new 

 plant may be formed in a similar way from an axillary bud 

 at any node of the runner. So the runner is a means of 

 multiplication, because it gives rise to one or more new 

 plants. A single strawberry plant may send out many 

 runners, and thus in time come to be surroimded by a 

 group of daughter plants. The white clover and some 

 violets also multiply by means of runners. 



224. Tendrils and Thorns. — Some plants have branch 

 tendrils — that is, tendrils that are really branches ; the 

 greater number of ten- 

 drils, however, are leaf 

 tendrils. Sometimes, in 

 plants with branch ten- 

 drils, each tendril is a 

 single long internode. 

 This is true of the pas- 

 sion-flower. But in other 

 plants, such as the Vir- 

 ginia creeper (Fig. 128, 

 A), a tendril consists of 

 several nodes and inter- 

 nodes and may itself bear 

 very small leaves from 

 whose axils grow branches that are also tendrils. It is 

 not certain whether the tendrils of the cucumber and its 

 relatives are branches or leaves. The growing point of a 

 tendril, Hke that of a climbing stem, has a marked nutation. 

 In addition, when any part of the tendril comes in contact 

 with a solid object, the pressure acts as a stimulus that 



A B 



Fig. 128. — The Virginia creeper (A), 

 and the nearly related Japanese ivy (B), 

 showing how tendrils may assist in climb- 

 ing. After Kerner. 



