66 THE LIFE OF THE PLANT 



itself when the sheets are moistened. These examples 

 are quite sufficient to illustrate the action of vegetable 

 ferments. A similar effect is also produced by diastase, 

 which is easily obtained from malt liquor, i.e. liquid 

 obtained from germinating grain. One part of this 

 diastase dissolved in water is sufficient to turn into sugar 

 more than a thousand parts of starch ; the warmer the 

 liquid the more quickly does this transformation take 

 place. 



Thus the nutrition of the embryo of the seed by means 

 of the starch stored in its endosperm or cotyledons 

 becomes quite comprehensible. It is curious that this 

 process is exactly similar to that which takes place 

 during the nutrition of an animal organism. The saliva, 

 and the gastric and other juices secreted by the alimen- 

 tary canal, contain ferments which like diastase change 

 starch into sugar. It is quite easy to realise this : 

 if we suck a piece of bread a little longer than usual, we 

 notice a sweet taste. Thus both animals and plant- 

 embryos can make use of insoluble starch by changing 

 it into soluble sugar. 



A similar change must also take place in seeds, like 

 coffee beans or date seeds, with hard and horny endo- 

 sperms. The character of the endosperm is in such seeds 

 due to the very hard cellulose walls of the cell. During 

 germination this cellulose dissolves and serves to feed 

 the embryo. This dissolution aroused the suspicion 

 that a special ferment was concerned, and the existence 

 of such a ferment has since been proved. 



Let us pass to the second group of foods stored up in 

 the plant, to the albuminoids. In wheat grains and 

 flour, as we have already seen, they are present in the 

 insoluble and therefore immobile form of gluten ; but 

 even soluble albumens, such as the white of a hen's egg, 

 or the soluble albumen that occurs in vegetable endo- 

 sperms, are immobile, because they are colloids, i.e. 

 substances which do not pass through membranes, 



