THE SEED 65 



microscopic investigation answer this question. The 

 former shows that throughout the germination of the 

 seed the quantity of starch contained in it decreases. 

 The latter reveals a change in the starch grains : they 

 lose their characteristic form, appear as if corroded, and 

 sometimes break into pieces like ice that has been 

 thawed. They do, in fact, dissolve away. 



Now let us try and explain the reason for such a 

 transformation of starch into sugar. We can produce 

 this transformation artificially by using sulphuric acid ; 

 but seeds cannot obtain any free sulphuric acid. A 

 special substance called diastase appears instead of it 

 during the period of germination, producing on starch 

 quite a similar effect. Diastase may serve as a repre- 

 sentative of a whole group of substances generally called 

 ferments. The word ' ferment ' usually denotes a 

 substance which when used in a minute quantity is 

 able to produce the chemical transformation of other sub- 

 stances. There are many such ferments. Bitter almonds, 

 for instance, in themselves have no characteristic taste 

 or scent ; these qualities are produced in them by means 

 of a ferment, which begins to act as soon as the seed is 

 brought into contact with water. Mustard seeds, too, 

 would not have their pungent odour and taste unless 

 they contained the ferment, myrosine, which with water 

 decomposes a substance contained in them (the salt of 

 the so-called myronic acid) and liberates the pungent 

 mustard-oil. A very curious experiment demonstrates 

 this phenomenon. Chemists sell mustard plasters which 

 consist of two sheets of paper, to be laid one upon the 

 other and then moistened with water. Neither leaf by 

 itself constitutes the mustard plaster, but the character- 

 istic pungent odour of mustard is produced as soon as 

 they are brought in contact with each other. This is 

 because one of the sheets is smeared with the ferment 

 and the other with the substance upon which the 

 ferment acts ; the effect of the ferment only manifests 



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