68 THE LIFE OF THE PLANT 



mucilage secreted by the hairs with which the leaves 

 of this plant are covered and which seize upon the insects, 

 contains a substance apparently similar to pepsine. This 

 substance, in the presence of an acid produced by the 

 hairs of the sun-dew when irritated, like gastric juice 

 has the power of rendering albuminoids soluble. Insects 

 which, in the natural course of things, fall on these leaves 

 and fragments of meat or white of egg placed upon the 

 leaves, as in Darwin's experiments, alike become dissolved 

 and assimilated by the plant. These experiments which 

 proved that it is possible to feed a plant with insoluble 

 albuminoids led scientists to look for ferments like 

 pepsine in germinating seeds. Their discovery was not 

 long delayed. Such ferments were found first in 

 leguminous plants, and then in others such as hemp 

 and flax, and, lastly, in malted barley. A ferment 

 very similar to gastric juice in its effects has also been 

 discovered in the latex of Carica papaya. The nutrition 

 of the embryo at the expense of the stores of albuminoids 

 is now comprehensible : the pepsine-like ferment which 

 develops during germination acts upon the albuminoid, 

 transforming it into a soluble, diffusible form. In addi- 

 tion a certain quantity of albuminoid matter undergoes 

 a still greater transformation during germination, into 

 bodies capable of crystallisation — i.e. into crystalloids — 

 which diffuse still more readily. 



Thus the embryo of a grass seed, for instance, not only 

 feeds upon the same starch or gluten that we use in 

 eating bread, but also digests them in the same way as 

 we do ; treats them with similar ferments, and changes 

 them into glucose and peptones. We know less about 

 nutrition at the expense of the stores of fatty substances, 

 though we have some indications in this direction also. 

 Oils as such are generally unable to pass through cell- 

 walls moistened with water. They consist, however, 

 of so-called fatty acids in combination with glycerine, 

 a substance easily soluble in water ; and certain facts 



