350 



LINACEJE, OR FLAX FAMILY 



A small family of herbs and shrubs having perfect, regular, 4- 

 to 6-merous, hypogynous and nearly symmetrical flowers. The 

 fruit is usually a capsule, containing 1 or 2 seeds in each locule, there 

 usually being twice as many locules as there are styles. Of special 

 anatomical interest is the mucilaginous epidermal layer in the seeds 

 and leaves of Linum. Calcium oxalate is secreted only in the 

 form of solitary crystals. The non-glandular hairs are of the unicel- 

 lular type. Glandular hairs when present always have a multi- 

 cellular stalk. The tracheae usually have simple pores and the 

 sclerenchymatous fibers are generally marked by bordered pores. 



LINUM. Linseed or Flaxseed. The seed of Linum usitatissi- 

 mum (Fam. LinacesB), an annual, which is cultivated in nearly all 

 temperate and tropical regions, either for the fiber (flax) or seed. 



Description. Anatropous, ovid or oblong-lanceolate, flattened, 

 somewhat less rounded on one side and on one margin, summit acute 

 or beaked, chalazal end rounded, plano-convex in cross-section; 

 from 4 to 5 mm. in length, 2 to 2.5 mm. in breadth, 0.5 to 0.75 mm. 

 in thickness; externally light brown, very smooth and glossy, the 

 raphe extending as a distinct, light yellow ridge along one edge, 

 outer wall of epidermal cells transparent, mucilaginous and swelling 

 in water; easily cut; endosperm white, adhering to the seed-coat, 

 embryo light green, straight, 3 to 4 mm. in length, 1 to 2 mm. in 

 breadth, cotyledons plano-convex; odor slight; taste mucilaginous 

 and slightly unpleasant. 



Inner Structure. (Fig. 152). A thin mucilaginous epidermis; 

 two layers of parenchyma which overlie a continuous ring of stone- 



FIG. 152. Transverse section of flaxseed: E, epidermal cells with small lumina 

 and very thick outer wall showing mucilage lamellae; PY, PO, parenchyma 

 cells; ST, stone cells; P, parenchyma beneath stone cells; 0, obliterated 

 cells; CO, cells with reddish-brown contents; EN, endosperm. 



cells having yellowish, porous walls and rather large lumina; a 

 pigment layer, the cells having a reddish-brown content; endosperm 



