CHAPTER XI 

 HOW THE PLANT TAKES IN THE SOIL WATER 



135. PLANT-FOOD. Having learned what a plant is and 

 having seen it as a whole, we may now inquire how it 

 secures food with which to live. We can discuss only the 

 outlines of the subject here : the pupil may consider the 

 question again when he takes up Part III. The plant 

 obtains food materials from the soil. We know this to 

 be true, because the plant dies if removed from the soil. 

 In this discussion, we use the word food to designate any 

 material which the plant takes in to incorporate with its 

 tissues or to aid in promoting its vital activities. The word 

 is sometimes used to denote only some of the products (as 

 starch) which the plant manufactures from the raw ma- 

 terials, but it is unfortunate to press a common -language 

 word into such technical use. 



136. ROOT STRUCTURE. - 

 info the thinnest and finest 

 there are roots and there are rootlets. 

 The large, fleshy root of the radish 

 (Fig. 103) terminates in a common-sized 

 root to which little rootlets are at- 

 tached. Then there are little rootlets 

 attached to the fleshy root at various 

 places near the base. But the rootlets 

 which we see are only intermediary, 

 and there are numerous yet smaller , 



^ 103. Root and rootlets. 



structures. 



137. The rootlets, or fine divisions, are clothed with root- 

 hairs (29), which are very delicate structures. Carefully 



(64) 



