510 WEED FLORA OF IOWA 



posed of rectangnlar cells resembling those of the mesophyl. Both 

 of these layers become more or less obliterated at maturity and are 

 of no diagnostic importance. 



Pericarp. The ventral side is flat and has a darker colored spot, 

 the remains of the hUum, near the base. Extending half way from 

 the base to the apex on the dorsal side is a groove, which marks 

 the position of the embryo. Vogl describes minutely the histology 

 of the caryopsis of common millet {Panicum miliaceum L.) and 



Fio. 387. Green Foxtail. Outer epidermis from the edge of the glume of the 



fertile flower. X 300. 



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



states that German millet {Setaria panis Jessen) has practically 

 the same structure. I find that his description applies also to the 

 caryopsis of both green and yeUow foxtail. 1. Epidermis. As in 

 the outer epidermal layers of the floral envelopes the cells axe 

 elongated and wavy in outline. On the dark colored spot already 

 referred to, the epidermal cells are more or less rectangular. 



2. The Cross-Cells are similar to the tube-ceUs in form but are 

 usually shorter, broader, and more irregular in shape. 3. Tube- 

 Cells. These are 0.002 to 0.004 mm. wide and often reach the 

 length of 0.3 mm. a. Nucellar or Hyaline Layer. After treatment 

 with alkali, this layer is clearly seen in surface view. The cells 

 are of large size and have beaded walls, h. Endosperm. 1. Aleurone 

 Layer. The cells vary in diameter from 0.01 to 0.02 mm. 



