THE SEED 67 



In order to pass from one cell to another, and thus to 

 serve as food to plants, albuminoids must go through a 

 transformation similar to the transformation of starch 

 into glucose. 



The study of the nutrition of an animal organism 

 will give us once more the key to the explanation of the 

 phenomena which take place in a germinating seed. 

 Gastric juice contains a ferment called pepsine, which 

 with a few drops of an acid has the property of turning 

 insoluble albuminoids into soluble ones ; for instance, the 

 white of a boiled egg, or the albumen of cooked meat, into 

 soluble substances, called peptones. These are not only 

 soluble in water, but are also capable of passing through 

 animal and vegetable membranes. For a long time 

 nothing of the kind was ever observed in the vegetable 

 world, and so long the translocation of albuminoids 

 remained unexplained ; but at last almost simultaneously 

 discoveries were made in totally different directions 

 which demonstrated the transformation of albuminoids 

 in vegetable organisms. 



Even as early as the eighteenth century a plant called 

 the ' Catch-fly ' had been observed to seize, by means of 

 its irritable leaves, insects which came into contact with 

 them in their flight and then use them as food. This 

 fact, however, had not been sufficiently appreciated : 

 the sceptical even cast doubts upon the existence of the 

 phenomenon, and it might eventually have been quite 

 overlooked had not Darwin paid attention to it. Dar- 

 win added considerably to the list of such carnivorous 

 plants, and acquainted botanists with curious details as 

 to their functions. We shall postpone to a future 

 lecture the description of the mechanical side of such 

 phenomena, and here consider them only in so far as they 

 illustrate the fact of a plant's capacity for using as food 

 an insoluble albuminoid. These phenomena of digestion 

 in plants were studied by Darwin more especially in the 

 sun-dew, a plant fairly common in marshes. The 



