MICROSCOPIC STRUCTURE OF WEED SEEDS 



511 



2. Starch-Cells. Polygonal starch granules with conspicuous hilums 

 fill the parenchyma cells of the endosperm. In the outer layers 

 they are from 0.004 to 0.008 mm. in diameter but farther inward 

 they reach the maximum diameter of 0.018 mm. After dissolving 

 the starch with potash, there remains a network of threads con- 

 taining conspicuous granules. In this respect, however, this fruit 

 cannot be distinguished from the fruits of S. glauca Beauv., 

 S. panis Jessen, Panicum miliaceum L. (see Vogl) and all the 

 other species of Panicum which I have examined. Detection in 

 Powder Form. The membranous glumes with pores in the bends of 



Fig. 388. Green Foxtail. Transverse section of caryopsis. F, pericarp con- 

 sisting of the epidermis ep and the tube-cells sch ; N, nucellar layer ; E, 

 endosperm consisting of the aleurone-cells al and the starch cells s. X 300. 

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



the walls and the coriaceous, transversely wrinkled, more or less 

 spotted, envelopes of the fertile flower with compoundly sinuous, 

 thickened cell walls are highly characteristic of both green and 

 yellow foxtail. These tissues are usually present in all stages of 

 development. The fruit elements are like those of common millet 

 and German millet. Treatment with caustic alkali brings out the 

 structure of the fruit coats and nucellar layer, and serves to dis- 

 tinguish this fruit from the common cereals. The starch is hardly 

 distinguishable from the starch of bindweed. 



Dr. A. L. Winton describes the microscopic character of yellow 

 foxtail {Setaria glauca Beauv.) as follows: 



The fruit of this species is larger than that of green foxtail, the 

 envelopes are also proportionately larger (with the exception of 

 the upper empty glume which is but half the length of the 



