ON THE STRUCTURE OF THE ROOT. 67 



there is great poverty of floral types in rapidly-flowing waters, 

 compared with their abundance in still and quiet waters. Nor is 

 the reason of this far to seek. All the particles in the water at 

 the same place move at the same rapid rate, and it is impossible 

 for a plant to select and absorb its food when placed under the 

 resulting mechanical disadvantage, as sufficient time is not allowed 

 for the act of absorption to take place. Moreover, even if this 

 necessary act could be performed under the circumstances, it is a 

 well-ascertained fact that water from natural sources contains a 

 scarcity of those salts which can be assimilated by the plant as 

 food. 



®n the Structure of tbe IRoot. 



By Harold Wager, F.L.S., 



AND 



Norman Walker, 

 Assistant in the Biological Laboratory^ Yorkshire College.^ 



Plate IV. 



THE roots of plants perform two functions. First, they fix 

 the plant firmly in the soil and keep it upright ; and second, 



they absorb food substances in the form of water contain- 

 ing mineral salts in solution. We shall appreciate the importance 

 of the root when we remember that a plant is largely made up of 

 water in one form or another, for all the solid material in the plant 

 consists of water in combination with other substances, and a 

 large amount of what may be called free water fills up the 

 numerous spaces which occur in this solid structure. Now, very 

 little, if any, water is absorbed by any part of the plant except 

 the root. The water thus absorbed is ultimately carried upwards 

 to all parts of the plant. 



Furthermore, as the leaves absorb a certain kind of food — 

 carbonic acid gas — from the air, which food is transformed by a 

 series of chemical changes, first into sugar, then starch, and then 

 again into sugar, in which form it is dissolved and distributed to 

 other parts of the plant where such food is required, we must, 



* Paper read to the Leeds Naturalists' Club on Nov. i, 1895. 



