STRUCTURE OF SEEDS 



725 



them. Various points of interest respecting the structure of the 

 testa or envelope of seeds, such as the fibre-cells of Cobcea and 

 Collomia, the stellate cells of the star-anise, and the densely con- 

 solidated tissue of the 'shells' of the coquilla-nut, cocoa-nut, itc. 

 having been already noticed, we cannot here stop to do more than 

 advert to the peculiarity of the constitution of the husk of corn- 

 grains. In these, as in other grasses, the ovary itself continues to 

 envelop the seed, giving a covering to it that surrounds the test:i, 

 and closely adheres to it. The ' bran ' detached in grinding consists 

 not only of these two coats, but also (as the microscope reveals) of 

 an outer layer of the grain itself, formed of hexagonal cells disposed 

 with great regularity. As these are filled with gluten, the removal 

 of this layer takes away one of the most nutritious parts of the 

 grain ; and it is most desirable, therefore, that only the two outer 

 indigestible coats should be detached by the 'decorticating' process 

 devised for the purpose. The hexagonal cell-layer is so little altered 

 by a high temperature as still to be readily distinguishable when 

 the grain has been ground after roasting, thus enabling the 

 microscopist to detect even a small admixture of roasted corn with 

 coffee or chicory without the least difficulty. 1 



1 In a case in which the Author was called upon to make such an investigation, 

 he found as many as thirty distinctly recognisable fragments of this cellular enve- 

 lope in a single grain of a mixture consisting of chicory with only 5 per cent, of 

 roasted corn. 



