AGRICULTURE 



The -water current. The current of liquid rising from 

 the roots and soil soaks through tiny canals in the stem up 

 to the leaves. In trees, the tubes that carry water from 

 the soil upward are located in the sap-wood, while those 

 that bring the sap downward from the leaves to build up 



all parts of the plant lie between 

 the outer bark and the sap-wood. 

 If you cut off a branch of a 

 grapevine just as the buds are 

 swelling, you will notice next day 

 that the wound has "bled," that 

 is, water has been forced up to 

 and out of the cut portion. When 

 we speak of the sap rising in 

 the spring, we mean that the roots have 

 begun to force water upward. As soon 

 as the leaves appear, the real sap 

 will flow downward in the inner bark 

 at the same time that the water from 

 the soil continues to rise through the 

 tiny channels nearer the center of the 

 stem. 



Root-hairs. The large roots which 

 you easily see when you pull up a plant are not the ones 

 that absorb water from the soil. If you will carefully 

 dig up the smallest roots of a very young plant, you will 

 notice that the slenderest roots are covered near their ends 

 with a white coating like velvet. These white threads are 

 root-hairs (Fig. 27). It is the business of each of these 

 short, velvety threads, or root-hairs, to absorb moisture and 



FIG. 



27. ROOT-HAIRS 

 OF SQUASH 



