CHAPTER VII 



THE WAYS IN WHICH PLANTS DRAW INTO THEMSELVES 

 THE VARIOUS MATERIALS THEY NEED 



Absorption; Roots 



N the preceding chapters we have traced pretty fully 

 the principal processes occurring within the bodies of 

 plants. But as yet we have taken no thought of the 

 ways in which plants absorb the various materials they 

 need from outside; and this is the inquiry which now lies before 

 us. I give the reader fair warning that the subject will lead us 

 perforce into distant, unfamiliar, and recondite matters; but their 

 study will have the advantage of illuminating a good many things 

 besides absorption by plants. 



Of all the substances absorbed by plants, the foremost is water, 

 which not only makes up a great part of plant substance, but 

 is also indispensable for various physical and chemical uses. 

 This water is absorbed, as everybody knows, through the roots; 

 but the fact is less familiar that the absorption takes place ex- 

 clusively through the young white terminal parts. Upon these, 

 accordingly, we now center our attention. They can be studied 

 most easily, and without obscuration by adherent soil particles, 

 in young roots obtained by the germination of seeds in flower-pot 

 saucers kept shaded and wet. From such specimens it appears 

 that young roots as a whole are remarkably alike, and possess 

 several features in common, — viz., a slender white shaft with a 

 yellowish tip, and a diaphanous garment of delicate radiating 

 hairs, — features which are shown very well, except for the color, 

 in the seedling of Mustard pictured herewith (figure 52). If 



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