teRIGHtNESS ^37 



The chief causes of alterations in the colour are dampness, 

 age, and harvesting when unripe. Nearly all immature samples 

 show a tinge of green ; this is particularly the case with the 

 various species of clover, lucerne, black medick, and pale seeds 

 generally. Those of the cruciferous plants as cabbage, turnip, 

 and swede, which are naturally a very dark brown or black, 

 show a paler brown or reddish tinge when unripe. The purple 

 colour of red clover seed changes to a foxy red tint when they 

 are old, and yellowish seeds, such as lucerne and black medick, 

 become brownish after being kept ; dark coloured ones of the 

 crucifers changing to a dirty grey. 



The pale yellow colour of barley is rapidly darkened on 

 exposure to heavy dew or rain, and moisture in any form is a 

 frequent cause of altered colour of seeds. 



We see, therefore, that the examination of the tint of samples 

 of seeds may often reveal defects in them, but it is to be 

 remembered that various processes of dyeing and bleaching 

 discoloured seeds have been employed by fraudulent persons 

 in order to restore the colour and put them on the market as 

 fresh samples, or to use them in mixtures. 



(c) Brightness. — Fresh new seeds of some species of plants 

 have a very smooth, glossy epidermis or skin, and appear polished. 

 Clovers have this natural brightness in high degree, while some 

 of the nearly related leguminous plants, e.g., lucerne and black 

 medick, show very little of this peculiarity. As an indication of 

 quality it is only of limited application, but in seeds which 

 are naturally bright, a dull appearance is a sign of age, bad 

 harvesting, or injurious storage. Oil is sometimes used in 

 order to impart brightness to old and bad seeds; very little 

 indeed is needed to put a completely deceptive appearance on 

 them, and suspicious cases should be tested. If much oil has 

 been employed, shaking the seeds with water often reveals it 

 as on standing it floats in drops on the surface of the water. 

 A more accurate method is to place the seeds in a flask con- 



