CLIMBING AND WATER PLANTS 111 



growing points. Consequently the stem is 

 gradually falling downwards as the older 

 anchoring branches die and rot away. A 

 further cause of the same slackening of the 

 stem is to be discovered in some climbers, 

 depending on the odd circumstance that the 

 growth in length of the stem continues long 

 after it would ' have ceased in ordinary 

 plants. 



The general effect of this elongation of the 

 stem below the forest roof, in whatever way 

 it is produced, is to relieve it entirely of all 

 danger from tensile stress. Hence the stem 

 can now, to the great advantage of the plant, 

 become almost entirely concerned in provid- 

 ing the means for the transmission of water 

 from the roots to the mass of foliage above. 

 A secondary consequence also is to be seen 

 in the development of the other tissues by 

 which the food material manufactured by 

 this foliage is distributed in the plant. If 

 much of it is withdrawn to the roots the stem 

 is rich in phloem, but it is not especially 

 so if, as is generally the case, most of the 

 manufactured food is immediately utilised 

 in the copious production of flowers and fruit. 



The structure of such specialised climbers 

 as these is capable of being interpreted as 

 the result of a compromise, so to speak, 

 between the opposing functions of nutrition 

 and mechanics. The compromise is more 

 obvious than in the majority of land plants 

 because the issues are more strictly defined. 



