CH. VIIl] INTERXODES OF CLIMBERS 101 



the short-stemmed rosette-plants to the woody tree, palm 

 or bamboo, Avhich may easily be referred to the type, but 

 differ according to the length, strength, and duration 

 of the internodes, and the amount of branching they 

 undergo. 



In climbing plants, however, the additional fact comes 

 in that a support is needed for the shoot. The latter 

 may be quite typical as regards its parts, but the 

 elongated internodes are not stout nor rigid enough to 

 stand alone and bear the weight of the foliage ; and in 

 accordance with this fact these plants make use of other 

 solid objects — other plants, rocks, &c. — to climb up. The 

 well-known fact that all these climbing plants begin life 

 with typical, self-supporting, erect shoots suggests that 

 the feebleness of the elongated internodes of so many of 

 them is the derived character consequent on the acquire- 

 ment of the climbing habit, and as'there is [dubious] experi- 

 mental evidence to show that additional strains in stems 

 bring about the construction of mechanical tissues, we may 

 probably look on the climbing shoot as having sacrificed 

 strength of internodes, which has become unnecessary, to 

 length, which is an advantage where it leads to the 

 exposure of the foliage high up above the thicket which 

 would otherwise dominate it. In a certain sense indeed 

 the weak elongated internodes of many climbers remind 

 us of the feeble dra-wn stems of plants which have grown 

 in too scanty a light, though I would not advise the 

 student to speculate upon an}' causal connection between 

 the two cases, but simply note that as with a long and 

 slender climbing plant so with a lanky "drawn" plant 

 the extra length of stem gained by the elongation of the 

 internodes increases the plant's chances of rising above 

 the surrounding plants and other objects and exposing its 

 leaves to the light and air. 



