514 



WEED FLORA OF IOWA 



up to 0.5 mm. or more. 3. Spongy Parenchyma. As seen in sur- 

 face view, the cells of this layer are more or less rectangular with 

 circular intercellular spaces and resemble those of rice and barley 

 glumes. 4. Inner Epidermis. In cross section this layer is not 

 readily studied since the radial walls are usually collapsed; but 

 in surface preparations, the large elongated cells, often 0.15 mm. 

 long and 0.05 mm. wide, interspersed with stomata and hairs, are 

 clearly displayed. 



Thin Glume. — Within the lower or first glume and nearly equal- 

 ing it in length, is the third or thin glume, the remnant of an 

 abortive flower. This glume is exceedingly thin and membranous 

 and bears numerous hairs, particularly in the margin. 1. Outer 

 Epidermis. In general form the cells are similar to those of the 

 outer epidermis of the thick glumes, but are narrower and much 

 thinner- walled. The marginal hairs are long (often 0.5 mm.) 

 single-celled and pointed; but on the surface shorter hairs, with 

 two or three joints and blunt ends, also occur. Both of these 



Fig. 392A Fig. 392B 



Fig. 392. Broom-corn. A. aep, outer epidermis and f, fiber of an empty glume 



in surface view. X 300. 



B. p, spongy parenchyma and iep, inner epidermis of an empty glume in surface 



view; sto, stoma; h, hair. X 300. 



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



