26 



usually be detected even when only small quantities of this sub- 

 stance are present in feeds. There are three microscopical charac- 

 teristics which serve to identify this product. The first is the 

 epidermal layer of cells which are very irregular in shape and 

 size, varying up to 70// in length. These cells have very thick, 



Figure 17 



Fig. 17. Cotton seed. (1) Epidermal cells; (2) Colorless "fringe 

 cells" of perisperm. (3) Palisade cells in cross and (1) longitudinal section. 



stratified walls of a yellowish color and a deep brown cell content. 

 Hairs with thickened walls and a dark interior are almost always 

 present and aid in the diagnosis. 



The palisade cells are next in importance ; they have a yellow- 

 ish brown color and in surface view appear polygonal, giving the 

 tissue a honeycomb appearance. More or less parallel lines cross 

 the cell but are sometimes difficult to see; in diameter these 

 cells are from 10 — 20/1 and have a length of about loO/i. 



Covering the embryo is found a thin layer of cells, the walls 

 of which are fringed, giving to the whole the appearance of a 

 network of lace. These are almost colorless and it is sometimes 

 difficult to find them in a sample, but they are highly charac- 

 teristic of cotton seed. Fig. 17 shows these cells as well as those 

 elements previously discussed. 



