A STUDY OF WHEAT. 



fied differently in order to fulfill some special object, for which they 

 were made. 



The principal framework of the straw is built up of such cells 

 as appear at D, very thin walled and hexagonal. These cells are 

 modified in shape as they approach both the inner and outer edge 

 of the figure. At the inner edge we see regular four-sided, thin- 

 walled cells; as they reach the outer edge we find the walls quite 

 thick and the cells also four-sided. The row of cells as seen at C y 

 form the epidermis of the straw, and is composed of a simple layer. 

 The outer edge of these cells is quite thick-walled, and forms the 

 cuticle. This cuticle is- what gives the smooth polish to the surface 



FIG I. CROSS SECTION OF WHEAT STRAW. 

 A, Vascular Bundles. B, Spiral Vessels. Drawn with Camera Lucida, X 75. 



of the straw. In some varieties of wheat this cuticle is much 

 thicker than in others. If the season is a long, cold, stormy one, or 

 if the wheat grows in a cold climate, the cuticle will be found to be 

 thicker and more leathery. The darker round portions of the 

 figure, as seen at A, are the woody portions of the straw, or, as they 

 are called, fibro-vascular bundles. The fine cells forming the most 

 of these bundles, are woody cells, while the large openings near the 

 center of these bundles are the cross sections of large vessels or 

 ducts that run the whole length of the straw. 



Figure 2 represents a longitudinal section of a vascular bundle. 

 The cells shown on either side of this bundle, at C, are the funda- 

 mental cells seen in cross section at D, Fig. i. The cells at B are 

 the woody portions seen at A, in Fig. i. They have very peculiar 

 little pitts covering their surface. The large vessels at A, Fig. 2, 



