MICROSCOPIC STRUCTURE OF WEED SEEDS 



567 



the testa, consisting of a single layer of cells, thin-walled. The 

 nucellus of whitish, elongated, rather thick-walled cells, the en- 

 dosperm differentiated into an outer layer of larger parenchyma 

 and a compressed inner layer of thick-walled cells. The epidermal 

 cells of the embryo nearly isodiametric, contain protein and fat. 

 The epidermal cells of the upper epidermis nearly like the lower, 

 palisade parenchyma underneath. 



Fig. 433. Microscopic structure of seeds of the Mint Family (Labiatae). 



I. Catnip (Nepeta cataria). II. Giant Hyssop (Agastache scrophulariaefolia). 



ep=epidermis, underneath, parenchyma cells in I and sclerotic parenchyma in 



II, the epidermal cells irregular showing some trichomes. scl=sclerotic 



parenchyma. en=endosperm. m=malpighian cells. n=nucellus. ll=light 



line. p=parenchyma. em=embryo. 



(Drawings by L. H. Paramel and C. M. King.) 



Giant Hyssop (Agastache scrophulariaefolia (Willd.) Ktze.). 



The small pubescent nutlet consists of the epidermal cells of 

 the pericarp with small unicellular thickened trichomes; cells con- 

 tain a brownish pigment; the cells of the layer underneath are 

 thick-walled, cell wall and cavity contain a brownish pigment. 

 The Malpighian layer follows, the cells being longer than wide, 

 the light line near the upper part of the cell. These cells are 

 yellowish. The testa is compressed and consists of elongated cells, 

 brownish in color. The endosperm varies in thickness, the cells 

 are in some cases elongated, in others squarish, and contain fat 

 and protein material. 



