77 CELL CONTENTS. 



white interior. The coats are better developed near the groove or 

 sinus of the seed. Mount hi glycerin or water. The sections can 

 be more easily prepared by soaking the grains for a few hours in 

 water. 



OBSERVE: 1. The form of the cells of the interior of the 

 grain. 



2. The form of the starch-grains in these cells. The stratifi- 

 cation is not often visible. It can be detected in some upon the 

 application of dilute Chromic Acid. This is a useful agent in 

 rendering the stratification of starch-grains, cell-walls, etc., more 

 distinct. 



3. The form of the Aleurone-cells (or " gluten sacs ") in- 

 closed by broad white walls, whose outlines may be traced even on 

 their peripheral side. The Aleurone-cells lie next to the starch- 

 bearing cells. 



4. The minute yellowish grains of Ati'm-nne filling these 

 sacs. 



5. The Seed-coats and the Ouary-coatK. ' 



(a) The Inner seed coat, (or Secundine) made up of two layers 

 of white homogeneous cellulose, separated by an interrupted gran- 

 ular line or thin layer. The peripheral of these two layers is 

 regarded as the true " Inner seed-coat." 



(b) The Outer seed-coat (or Primine], usually a narrow brown 

 band. In this lies the color of "red" and "white" wheat. 



(c) The Endocarp, apparently marked at intervals by oblong 

 transverse pits, pinkish from refracted light. The Endocarp con- 

 sists of a layer of elongated, thick-walled cells, running transverse 

 to the long axis of the grain, therefore parallel to this section. The 

 oblong pits referred to are narrow, nearly-closed passages through 

 the party walls between these cells. 



(d) and (e) The Exocarp. This is made up of several layers 

 (usually two) of oblong, thick-walled cells running parallel to the 

 long axis of the grain. The ends of these cells will therefore appear 

 in the present section as oblong openings. When first mounted they 

 are not always apparent. These thick-walled cells of the Endoc.-irp, 

 Exocarp, etc., are Sclerenchyma cells, and characteristic of the pro- 

 tective coverings of seeds. 



