190 THE StOKY OF THE t>LANT3. 



flowers, for which purpose it is often streng- 

 thened by means of mechanical woody tissue, 

 also acts as a conductor of raw sap from the tips 

 of the roots to the leaves and growing points, 

 for which purpose it is further provided with an 

 elaborate system of canals and vessels, running 

 direct from the absorbent root to all parts of the 

 compound plant community. 



The third function of the stem and branches 

 is to convey and distribute the elaborated pro- 

 ducts of plant-chemistry and plant-manufacture 

 from the places where they are made to the 

 places where they are needed for practical 

 purposes. 



I We saw long since that starches, sugars, pro- 

 toplasms, and chlorophyll are manufactured in 

 the leaves under the influence of sunlight ; and 

 from the materials so manufactured every part 

 of the plant must ultimately be constructed. 

 But we never said a word at the time about the 

 means by which the materials in question were 

 carried about and distributed to the various 

 organs in need of them. Nevertheless, a mo- 

 ment's consideration will show you that new 

 leaves and shoots must necessarily be built up 

 at the expense of materials supplied by the 

 older ones ; that flowers, fruits, and seeds must* 

 be constructed from protoplasm handed over 

 for their use by the neighbouring foliage. Nay 

 more ; the root itself grows and spreads ; and 

 the very tips of the roots, which themselves^f 

 course can manufacture nothing, must be sup- 

 plied from, above. with most active and discrimi- 



