CoGNiTic State of Energy 137 



hours, to spread over the nutritive substratum. It is for the 

 present purpose a matter of minor moment, whether we should 

 view such an organism as a plant or an animal. 



^Vhen we turn to the highest plants, cursory study of the 

 irritable phenomena might indicate a simple physico-chemical 

 explanation, such as the mere upsetting molecularly of a definite 

 organic substance, and, after the effect of the stimulus has 

 ceased, a gradual reestablishment of the molecular equilibrium. 

 But the conditions are much more intricate and fundamental. 

 Thus, when the tip of a leaflet of Mimosa pudica, the tentacle 

 of a Drosera leaf, or the hair of Dioncea is stimulated by mech- 

 anic, thermic, chemic, or electric energy, the stimulated cells 

 respond, as the writer has pointed out elsewhere (81: 205), by 

 change in the protoplasmic-chromatin pellicle, and almost 

 immediately thereafter by undergoing chemical decomposition 

 changes in the protoplasmic substance, so that the enclosed 

 "aggregation body" — itself a complex lipoproteid — squeezes 

 out water and contracts. 



Such changes are particularly well followed in Mimosa and 

 Drosera, in part by the naked eye, in part by the microscope. 

 Now one might readily suppose that the entire change centered 

 in, and was determined by, the aggregation mass within the 

 nucleo-protoplasmic sac, and not at all by the latter. But we 

 cannot then explain why the energy applied as a stimulus 

 passes j^r^^ through the enclosing and living sac; second, why 

 this living sac becomes porous to the passage of liquid; third, 

 why, after the effect of the stimulus has passed, the sac again 

 passes liquid inward to the aggregation mass, so as to cause 

 resorption by it of the liquid; fourth, why in time when the 

 mass has reestablished its former size and equilibrium the sac 

 becomes closed to liquid exudation and even shows high ten- 

 sion-conditions. 



Thus the rapidity with which a fallen Mimosa leaf will, 

 within five to eight minutes after stimulation, rise against 

 gravity and reexpand its leaflets is proof not merely of tension 

 strains between cells, but much more imi)ortantly of definite 

 flows and redistributions of energy in the chromatin and the 



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