SECTION 16.] TRANSFORMING MATERIAL AND ENERGY. 155 



and vigorous leaf, under a high summer temperature, and when the trap 

 lies widely open, a touch of any one of the minute bristles on the face, by 

 the finger or any extraneous body, springs tiie trap (so to say), and it 

 closes suddenly ; but after au hour or so it opens again. When a fly or 

 other small insect alights on the trap, it closes in the same manner, and so 

 quickly that the intercrossing marginal bristles obstruct the egress of the 

 insect, unless it be a small one and not worth taking. Afterwards and 

 more slowly it completely closes, and presses down upon the prey ; then 

 some hidden glands pour out a glairy liquid, which dissolves out the juices 

 of the insect's body ; next all is re-absorbed into the plant, and the trap 

 opens to repeat the operation. But the same leaf perhaps never captures 

 more than two or three insects. It ages instead, becomes more rigid and 

 motionless, or decays away. 



479. That some few plants should thus take animal food will appear 

 less surprising when it is considered that hosts of plants of the lower grade, 

 known as Pungi, moulds, rusts, ferments. Bacteria, etc., live upon animal 

 or other organized matter, either decaying or living. That plants should 

 execute movements in order to accomplish the ends of their existence is 

 less surprising now when it is known that the living substance of plants 

 and animals is essentially the same ; that the beings of both kingdoms par- 

 take of a common life, to which, as they rise in the scale, other and higher 

 endowments are successively superadded. 



480. Work uses up material and energy in plants as well as in ani- 

 mals. The latter live and work by the consumption and decomposition 

 of that which plants have assimilated into organizable matter through an 

 energy derived from the sun, and which is, so to say, stored up in the as- 

 similated products. In every internal action, as well as in every movement 

 and exertion, some portion of this assimilated matter is transformed and 

 of its stored energy expended. The steam-engine is an organism for con- 

 verting the sun's radiant energy, stored up by plants in the fuel, into me- 

 chanical work. An animal is an engine fed by vegetable fuel in the same 

 or other forms, from the same source, by the decomposition of which it 

 also does mechanical work. The plant is the producer of food and accumu- 

 lator of solar energy or force. But the plant, like the animal, is a con- 

 sumer whenever and by so much as it does any work except its great work 

 of assimilation. Every internal change and movement, every transforma- 

 tion, such as that of starch into sugar and of sugar into cell-walls, as well 

 as every movement of parts which becomes externally visible, is done at 

 the expense of a certain amount of its assimilated matter and of its stored 

 energy ; that is, by the decomposition or combustion of sugar or some such 

 product into carbonic acid and water, which is given back to the air, just 

 as in the animal it is given back to the air in respiration. So the respira- 

 tion of plants is as real and as essential as that of animals. But what plants 

 consume or decompose in their life and action is of insignificant amount in 

 comparison with what they compose. 



