THE STEM AND BRANCHES. 167 



bamboos, the stem does not increase in quite the 

 same way from within outward, and there are 

 therefore no rings of annual growth to judge by. 

 Palms rise from the ground as big or nearly as 

 big at the beginning as they will ever be in the 

 end ; and though each year they rise higher and 

 higher into the air, and produce a fresh bunch of 

 leaves at their summit, they seldom branch, and 

 they never produce large buttressed stems like 

 the oak or the chestnut. 



The second main function of the stem is to 

 convey the raw sap absorbed by the roots to the 

 leaves and branches, and especially to the grow- 

 ing points. This is such a very important element 

 in plant life that we must now consider it in some 

 little detail. 



If you look for a moment at a great spreading 

 oak-tree, with its top rising forty or fifty feet 

 above the level of the ground, and its roots 

 spreading as far and as deep beneath the earth, 

 you will see at once how serious and difficult a 

 mechanical problem it is for the plant to raise 

 up water from so great a depth to so great a 

 height without the aid of pump or siphon. For 

 the plant can no more work miracles than you or 

 I can. Yet every leaf must be constantly supplied 

 with water, that prime necessary of life, or it will 

 wither and die ; and every growing part must ob- 

 tain it in abundance, in order to give that plas- 

 ticity and freedom which are needful for the earlier 

 constructive processes. Protoplasm itself can ef- 

 fect nothing without the assistance of water as a 

 solvent for all materials it employs in its opera- 

 tions. 



How does the plant get over these difficulties ? 



