128 SEEDS. 



(65) Linseed 



The seeds of Linum usitatissinmm, Linn. (N.O. Lineae). 

 The seeds are covered with a glossy brown, finely pitted coat 

 in which the following layers can be distinguished : 



(1) An outer layer consisting of a single row of radially 

 elongated cells. These cells contain mucilage which rapidly 

 swells in contact with water. In surface view they appear 

 polygonal, with thin, smooth and straight or only slightly wavy 

 walls. 



(2) A parenchymatous layer (p) composed of two rows of 

 polygonal cells, which, in surface view, appear rounded and 

 rather thick-walled, and often exhibit small intercellular 

 spaces. 



(3) A sclerenchymatous layer (sc) consisting of a single row 

 of cells, which appear oblong or nearly square in section ; 

 in surface view they are long and narrow ; these cells have 

 thickened, pitted walls. 



(4) A hyaline layer (h) ; the cells of which this layer is made 

 up are very much flattened. The most easily visible of them 

 form a single row of long, narrow cells, with very thin walls, 

 crossing the sclerenchymatous cells at right angles. Here and 

 there a second row of similar, but less easily visible, cells may 

 be discerned crossing the previously mentioned layer at right 

 angles. In the powdered drug layers (3) and (4) almost always 

 remain united, and layer (2) is also generally attached to them 

 (SP). ' 



(5) A pigment layer (tc) consisting of a single row of flattened 

 cells with pitted walls. These cells are filled with a dark 

 brown homogeneous mass, which sometimes falls out intact ; in 

 surface view they are seen to be polygonal and isodiametric. 



The cells of the endosperm (alb) are polygonal and contain 

 aleurone grains and fixed oil ; those of the embryo are similar, 

 but are rather smaller and more regular. 



The aleurone grains are characteristic ; they are ovoid in 

 shape, and contain a very distinct globoid and one or two large 

 crystalloids. 



The diagnostic characters of powdered linseed are : 



(a) The pigment cells with pitted walls and amorphous 

 dark reddish-brown contents. 



(b) TJie sclerenchymatous cells, crossed at right angles by 

 delicate, colourless, elongated parenchymatous cells. 



(c) The thick- walled cells of the subepidermal layer. 



(d) The characteristic aleurone grains. 



