134 ELEMENTARY AGRICULTURAL CPIE^XISTRY 



the more branches and flowers the plants produce the better. 

 In the former case thick seeding, say 100 lb. per acre, is 

 employed, while for the latter from a quarter to half that 

 amount suffices. A fair yield of linseed in America is about 

 15 bushels of seed (of 56 lb. per bushel) and about 2000 lb. 

 of straw. The usual species (L. usitatissimiim)3ittsimssi height 

 of about two feet, and has blue flowers ; another species 

 {L. americanwn album) is somewhat taller, and has white 

 flowers ; while a third (L. crepitans), which produces much 

 seed but little fibre, scatters its seeds by the explosive bursting 

 of its capsules. 



Linseed is chiefly valuable for the oil which it contains 

 (from 30 to 40 per cent.) and for the large amounts of nitro- 

 genous and mineral matter, particularly phosphates, which are 

 also present in the seed, and which are left in the " cake " after 

 the oil is expressed. Linseed cake is thus highly prized for 

 cattle-feeding. 



Oil expressed from the seed obtained from the Baltic ports 

 is usually preferred for the manufacture of linoleum, paints, 

 (kc, since it has the power of absorbing the largest quantity of 

 oxygen. Oil is obtained from the seed by crushing it, and 

 then either expressing the oil by heat and pressure (old 

 process) or by extraction with volatile solvents — carbon 

 disulphide or naphtha (new process), in which the oil readily 

 dissolves. In the latter case the solvent is separated from the 

 oil by distillation and from the "meal" by steaming. The 

 "old process" meal usually retains from 8 to 12 per cent, 

 of oil, while the "new process" sometimes contains not 

 more than 1 or 2 per cent. Tho former is generally pre- 

 ferred for feeding purposes, as it is the more digestible. 



Hemi^seedj {Cannabis sativa), related to tlie hop {Humulus 

 lupulus) and to ramie, is cultivated both for the fibre yielded 

 by its stem and for its oily seeds. It is an annual, growing to 

 a height of eight or ten feet. It thrives best in a temperate 

 climate, and in any soil suited to maize. The yield of fibre 

 is from 500 to 1500 lb. per acre, of seed from 10 to 30 



