MICROSCOPIC STRUCTURE OF WEED SEEDS 



519 



The tissue is made up of irregular spongy-parenchyma cells, 

 usually transversely elongated with large, round or elongated inter- 

 cellular spaces. 



The Testa (S). — Consists of one layer of elongated brown cells 

 10-20 wide. 



Perisperm (N). — This layer is enormously developed. As may be 

 seen in cross section, the cells are 40-" thick, but the walls are so 

 swollen as to almost entirely obliterate the cavity. After soaking 

 for some time in 1 per cent soda solution they are evident in sur- 

 face view. 



Endosperm. — 1. The Aleurone Layer (al) is not of especial in- 

 terest. 2. The Starch-Parenchyma (st) is remarkable for the thick- 

 ness of the cell walls (often 10 thick) and the elliptical starch 

 grains 3-20/* in diameter. With proper illumination each grain 

 may be seen to have an elliptical hilum. 

 ep s 



Fig. 397. Chess. Elements of fruit in surface view. Significance of letters same 



as in Fig. 396. 

 (After Winton, Conn. Agr. Exp. Sta.) 



Wild Barley or Squirrel-tail Grass (Hordeum jubatum L.). 



The grain is adherent to the palet. The epidermis consists of 

 thick-walled, tangentially elongated cells, most of which are longer 

 than broad. In part the cells are developed into short conical 

 trichomes. The underlying cells are thick-walled with prominent 

 pore canals. The remainder of the adhering palet consists of thin- 

 walled cells much larger than broad. The pericarp as well as the 



