ENERGY IN PLANT-CELLS. 183 



brewer is ready to deliver his beer to the customer, he is painfully 

 aware that his goods are in anything but stable condition. Hence 

 beer for shipment is placed in oak quarter-barrels (kegs), bound with 

 many broad iron hoops, and made by shape and in every way as stout 

 and strong as possible. Prior to filling at the brewery, beer-kegs are 

 subjected to water-pressure of thirty-five pounds to the square inch, 

 and yet, notwithstanding care in construction and rigor in the test ap- 

 plied, beer-kegs will once in a while actually burst ; i. e., the strain 

 caused by internal pressure passes (probably far surpasses) the limit 

 of the test. Here then, again, we have a gauge by which to estimate 

 the energy of life's forces. The pressure is due to the evolution of 

 gas ; but the gas, as has been said, is disengaged only as a consequent 

 of vitality, of growth, and, at the moment preceding the explosion, the 

 cells are acting, the processes of growth accomplishing, under a press- 

 ure of not less than forty or fifty pounds to the inch. The yeast-cell 

 grows, pushes forth bud after bud, liberates particle after particle of 

 carbon dioxide, all under increasing pressure the further the process 

 goes, until at last at the supreme moment oak and iron can endure no 

 more — the barrel bursts ! Here no one can quote osmosis, although as 

 between the contents of the cell and the surrounding liquid osmosis 

 doubtless there is, as there was in the case of the maple ; but osmosis 

 is certainly not responsible for the gas-pressure under which the cells 

 are working. 



The illustrations cited certainly establish the truth of the propo- 

 sition with which we began, viz., that plant-cells may display actual 

 appreciable energy. Indeed, it would seem that no one could look in 

 upon the living streams of any transparent, active cell, as these sweep 

 within narrow limits in tireless ebb and flow, and not be convinced 

 that in some way at least life is the exponent of force. What that 

 force may be, no one can positively as of knowledge say. If we affirm 

 that the energy of the plant-cell is to be traced to the sun's rays, we 

 state but a partial truth. The sunlight simply continues an energy 

 already started, simply keeps the machinery wound up, or rather pre- 

 vents its running down, and we can conceive of no cell whose primary 

 energy is not derived directly from the nearest link of the infinite 

 chain preceding. 



Take now into consideration what we may call the directive energy 

 of the cell (call it accumulated habit, hereditary endowment, or what 

 you will), which determines the direction and the limits of the cell's 

 gi'owth, which locks within the compass of a single bit of protoplasm 

 the destiny of millions of succeeding living atoms, combining to the 

 accomplishment of most wonderful and varied functions, so that every 

 germ-cell at the least has its own individuality, its own future, its own 

 ideal, into which in the order of Nature it comes, and we begin to see 

 that, even were the physical energies of the cell cleared up, we are yet 

 as far off as ever from the solution of life's problem. As Emerson puts 



