MICROSCOPIC STRUCTURE OP WEED SEEDS 531 



PI — 



Fig. 408. Black Bindweed. Seed in surface view. Signiflcance of letters same 



as in Fig. 406. 

 (After Win ton, Conn. Agr. Exp. Sta.) 



Detection in Powder Form. — Characteristic of this fruit are 

 the papillae on the outer epidermis of the calyx and the epicarp 

 with sinuous cell walls and rows of warts. The outer epidermal 

 cells of the testa are sinuous in outline, like those of buckwheat, 

 but, unlike the latter, lare commonly elongated. Although the cross- 

 cells are morphologically the same as the spongy parenchyma of 

 buckwheat, they resemble more nearly in structure the tube-cells 

 of the cereals. The starch granules are not characteristic and the 

 network obtained after treatment with caustic alkali serves merely 

 as an indication that the seed belongs to a Polygonaceous plant. 



Buckwheat (Fagopyrum esculentum Moench.). 



The achenium consists of elongated epidermal cells with thick- 

 ened walls, underneath similarly elongated thick-walled sclerotic 

 parenchyma cells with pore canals. This layer contains the pig- 

 ment. The testa follows the pericarp and is differentiated into 

 an epidermal layer of yellowish brown walls, followed by smaller 

 thin-walled, parenchyma cells. The testa is much compressed ; the 

 albumen consists of an outer aleurone layer of small cells followed 

 by larger cells. The albumen cells contain compound starch 

 grains. 



