512 



WEED FLORA OF IOWA 



spikelet) and the wrinkles on the glume of the fertile flower are 

 more pronounced. In microscopic structure the fruits of the two 

 species are identical. The floral envelopes are also much alike, 

 the only distinction being in the distance apart of the wrinkles on 

 the mature flowering glumes. In green foxtail this distance is 

 usually from 0.03 to 0.06 mm., but in yellow foxtail it is often 

 from 0.08 to 0.12 mm. Since this distinction does not apply to 

 the mature glumes and since the wrinkles on the palets of the two 

 species are practically the same, it is often difficult to identify the 

 species in ground mixtures. Fortunately, identification of the 

 genus is all that is usually required. 



sch -N 



Fig. 389. Green Foxtail. Caryopsis in surface view. Significance of letters 



same as in Fig. 388. 

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



Broom Corn {Andropogon sorghum var. technicus Koern). 



Dr. A. L. Winton describes the microscopic structure of the 

 pericarp and testa of broom com as follows: 



Empty Glumes. — Both glumes are from 4 to 6 mm. long, equal- 

 ing and closely enveloping the fruit. They vary in color from 

 yeUow-brown to red-brown. The soft hairs, which nearly cover 

 the outer surface, are loosely attached and most of them are re- 

 moved during the threshing and cleaning of the seed, leaving the 

 glumes smooth and shining. 1. The Outer Epidermis consists of 

 strongly selerenchymatized cells several times as long as they are 

 broad, with wavy contour, interspersed here and there with iso- 

 diametrie hair-scars, each accompanied by a crescent-shaped ceU 



