10 



A STUDY OF WHEAT. 



are the same as those seen in the cross section at B, Fig. i, only 

 magnified many times more. 



The spiral bands arranged so beautifully around these vessels 

 are little fine tubes, coiled around on the inside of the large vessels, 

 and growing firmly to the inside wall. Water or moisture is carried 

 the length of the straw by this spiral tube, as well as being absorbed 

 through the cell walls. 



FIG. 2. LONGITUDINAL SECTION OF WHEAT STRAW. 



Showing a Vascular Bundle. A, Spiral Vessels. B. Pitted Vessels. C, Regular 

 Parenchymatous Cells. Drawn with Camera Lucida, X 375. 



The only object of the woody portion of the straw is to give 

 strength enough to the plant to hold up its head until the wheat is 

 ready for the harvest. The spiral vessels and woody portions do 

 not, as many suppose, carry all the sap through the plant. The sap 

 is carried right through the cell walls by absorption, principally by 

 those cells found at C, Fig. 2, and at Z>, Fig. i. In order for the 

 sap to be raised one inch, it is obliged to pass through over two 

 thousand of these cells. 



Fig. 3 shows the epidermis covering the outer surface of the 

 straw. It has been torn off lengthways, and is the single layer of 

 cells seen at C, Fig. i. The long, narrow cells at B make up the 



