150 



SEEDS 



as well as cloth woven from flax, have been found in Egyptian tombs, 

 and the process of weaving is depicted on their buildings. The seeds 

 were used as a food ; the medicinal use of the mucilage and the value 

 of the oil contained in them appear not to have been known till later. 

 The flax plant bears a small globular capsular fruit containing ten 

 seeds ; these are separated when ripe. Argentina, Russia, Canada, 

 India, the United States and Holland furnish the principal supplies. 



Description. The seeds are commonly dark brown in colour, 

 smooth and shining. They are elongated ovoid, flattened, with an 

 acute edge ; from 4 to 6 mm. long. One end is rounded, but the other 

 has an oblique point, on one side of which, just 

 below the apex, is a slight depression. In this 

 depression both hilum and micropyle are situated, 

 the seed being anatropous. The surface of the seed 

 is glossy and minutely pitted. A transverse section 

 exhibits a yellowish white oily kernel consisting of 

 two large cotyledons surrounded by a narrow en- 

 dosperm (not always easily seen). Soaked in water 

 the seeds lose their glossy appearance and become 

 covered with mucilage. They have but a slight 

 odour, and an oily, mucilaginous taste. 



Both in colour and size linseed exhibits notable 

 variations according to its source. As a general 

 rule, warm climates yield larger and paler seeds 

 than cold climates. 



The student should observe 



FIG. 86. Linseed. 

 Transverse sec- 

 tion, showing the 

 seed-coats, endo- 

 sperm, and coty- 

 ledons. Magni- 

 fied. (Moeller). 



(a) The glossy pitted surface, 



(b) The mucilage extracted by water, 



(c) In the transverse section the two oily 



cotyledons and narrow endosperm 

 (under a powerful lens). 



Constituents. Linseed contains from 30 to 40 per cent, of fixed 

 oil, about three-fourths of which can be extracted by pressure. The 

 epidermis of the seed-coat contains mucilage (6 per cent.), which, 

 together with the proteids (25 per cent.) present in the seed and part 

 of the oil, are left in the cake obtained when the seeds are pressed. 

 The presence of oil, proteid, and carbohydrate (mucilage) in the cake 

 renders it valuable as a cattle food. Unripe seeds contain numerous 

 small starch grains, but the ripe seeds are free from starch. The 

 seeds also contain a cyanogenetic glucoside, linamarin, identical with 

 phaseolunatin (compare p. 38). 



The fixed oil (Oleum Lini, B.P.) consists chiefly of linolein, a mixture of the 

 glyceryl esters of linolic, linolenic, and isolinolenic acids, the acids themselves 

 being sometimes designated as linoleic acid ; it also contains similar esters of 

 oleic, stearic, palmitic, and myristic acids. On exposure to the air it slowly 



