MICROSCOPIC STRUCTURE OF SEEDS. 403 



tropa, Orchis, Parnassia, Pyrola, Saxifraga. 1 The seeds of Um- 

 ,belliferous plants generally are remarkable for the peculiar vittce, 

 or receptacles for essential oil, which are found in their coats. 

 Various points of interest respecting the structure of the testce or 

 envelopes of seeds, such as the fibre-cells of Cobcea and CoUomia, 

 the stellate cells of the Star-Anise, and the densely consolidated 

 tissue of the "shells" of the Coquilla-nut, Cocoa-nut, &c., having 

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

 to the peculiarity of the constitution of the "husk" of the Corn- 

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

 to envelope the seed, forming a covering to it, that surrounds its 

 own testa; this covering (which forms the "bran" that is de- 

 tached in grinding) is composed of hexagonal cells of remarkable 

 regularity and density ; and these are 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 very small admixture of roasted Corn with Coffee 

 or chicory, without the least difficulty. 2 



1 These lists have been chiefly derived from the " Micrograph io Dictionary," p. 572. 



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

 he found as many as thirty distinctly recognizable fragments of this cellular envelope, 

 in a single grain of a mixture consisting of Chicory with only 5 per cent, of roasted 

 Corn. 



