30 A STUDY OF WHEAT. 



of the plant. This single individual would, in several years, 

 produce quite a growth. Then there are changes produced in 

 a plant by the nature of its food and other external condi- 

 tions. Specimens of the same kind will differ very conspicu- 

 ously in the size and number of their leaves, flowers and fruits, 

 according as their supply of food has been abundant or defi- 

 cient. Deep shade frequently produces the most striking 

 change in the habits of wheat when they are accustomed to 

 grow in the sunlight, as all farmers can testify. These prac- 

 tical questions are studied carefully by farmers whenever they 

 wish to produce any particular variety of wheat. 



Unfortunately, it is not known to what country we are 

 indebted for the primitive plant of wheat. One of the greatest 

 botanists (De Candolle) claims that the original grass from 

 which wheat has been produced is yet growing in some ob- 

 scure locality in Central Europe. However, it is the oldest 

 cereal known, having been used in the very earliest time. So 

 probably varieties have been in existence and disappeared. 

 Perhaps the same variety has come and gone on the world's 

 stage many times, for there are at the present time many dif- 

 ferent varieties growing in the various countries of the world. 

 It is one of the easiest plants in which to produce variations. 



The microscope reveals differences in these varieties, which 

 are of more interest to the miller than are the physical ap- 

 pearances. 



The different varieties of wheat are constructed on the same 

 general principles, and indeed the resemblance is so strong that 

 any variety, no matter how far removed from the typical form, 

 can be identified as wheat under the microscope, however finely 

 it may be pulverized. The principal difference between the 

 varieties is in the size of . the different parts ; as, for example, 

 the size of the starch grains, the amount of cellulose packed on 

 the cell-walls, or the thickness of the different coats. The 

 examination and the measurements for this work have been made 

 with considerable care, while the illustrations are all drawn with 

 the camera lucida, so there can be no chance for the author's 

 imagination to play any part in the drawings. (A camera lucida 

 is an instrument which, by means of a prism or glass set at a 

 certain angle, the image of the object in the microscope may 



