INSECTIVOROUS PLANTS. 



405 



In order to assimilate them, the embryo secretes ferments of 

 different kinds, one called "diastase" converting two thousand 

 times its volume of starch into sugar ; another changes the solid 

 aleurone into an assimilable peptone ; while a third enables oil to 

 become emulsionised. In each case the process appears to be 

 identically the same as in our own digestive organs. 



As instances of other leaves secreting digestive fluids than 

 those of insectivorous plants, may be mentioned the leaves of the 

 Papaw and Fig trees. Mr. Henslow mentioned that in some 

 tropical countries it was a common habit to wrap up tough meat 

 in the leaves of the former, which soon began to secrete a fluid 

 which, by bringing about incipient digestion, rendered the meat 

 tender. The principle called papaine had been extracted from 

 the juice of the fruit and utilised in the form of digestive pills. 

 It had also been found efficacious in dissolving the false fungoid 

 membrane in diphtheria. 



Another example was to be seen in the formation of roots ; 

 for, when new ones are formed, they take their rise from certain 

 spots in a special layer called the " pericycle " within the interior 

 of the mother-root. The young root has a so-called " digestive 

 pocket " at the apex, which dissolves and absorbs the cortical 

 tissue of the mother-root until it makes its exit at the surface. 



Again, parasitical fungi which penetrate the tissues of stems, 

 leaves, tubers, and even solid wood, are enabled to do so by 

 secreting ferments which dissolve those tissues, however hard 

 they may be, and enable the slender tubes to penetrate and feed 

 upon them. 



Lastly, it occasionally happens that underground stems of 

 grasses meet with tubers or bulbs in their course, and, instead of 

 passing round, they burrow through them. It has lately been 

 discovered that the presence of the organised body induces the 

 apex of the shoot to secrete a ferment, which dissolves the tissues, 

 and so enables the grass-stem to literally bore its way through 

 the tuber. 



Mr. Henslow concluded his remarks by observing that these 

 few instances show how general is the process of ferment-action — 

 a vegetable rennet or cheese-forming ferment having even been 

 discovered — and that it would seem to be in no appreciable way 

 different from the kindred digestive processes in the animal 

 kingdom. 



