THE MICROSCOPICAL STRUCTURE 



OF THE DIFFERENT COATS. 



WOULD you believe there was any great complexity in the struc- 

 ture of a grain of wheat in looking at it with the naked eye? 

 for certainly it looks like the most simple thing in the world. Yet that 

 very little grain possesses a mechanism even more complicated and 

 curious than the structure of the most elaborate machinery. It 

 would be impossible to produce it artificially. No mechanical work 

 would be able to produce the delicate tracings or the minute cell 

 divisions which the microscope shows to be so beautiful. Neither 

 could it produce the nearly transparent covering, so delicate, so 

 thin, and yet so strong and tough, as to bravely withstand the 

 effects of moisture. That the wheat is minute as well as intricate 

 in its structure, we shall see before we are through with this study. 

 A grain of wheat is oval or egg-shaped, with a deep longitu- 

 dinal furrow on the inner face; with a keel or irregularly curved 

 surface covering the embryo on the back near the base of the grain, 

 and with quite a heavy growth of vegetable hairs at the opposite 

 end or the apex. It must be remembered that a grain of wheat is 

 not a seed as so many think, but rather a perfect fruit enclosing the 

 seed within itself, so necessarily its structure is more complex. 

 Starting from the outside of the kernel, let us see what different 

 structures we find before reaching the center. First, there are 

 three fruit coats known as the first, second and third fruit-coats, 

 then there are two seed-coats known as the first and second seed- 

 coats. This makes five distinct coats surrounding a grain of 

 wheat, which, taken all together, have a thickness of,, less that 1-15 

 of a millimeter (1-400 of an inch). Then we come to a coat as 

 thick or thicker than these five coats, containing the nitrogenous 

 substances. Then the -whole central mass of the grain loaded with 

 starch, and last the embryo at the base. It may make this clearer 

 if the different parts are tabulated as follows: 



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