906 



SCIENCE 



[N. S. Vol. XXVIII. No. 730 



of unicellular plants. A constant evapora- 

 tion at the surface might perpetuate the 

 differences of density sufficiently to con- 

 tinue the circulation for the requisite 

 period. So, on the other hand, if the 

 ground waters were sufficiently saline, the 

 periodic accession of fresh water at the 

 surface might give, in reverse order, 

 density-differences sufficient to perpetuate 

 circulation. 



"Whether analogy may be pushed so far 

 as this on substantial grounds or not, it is 

 obvious that the soil presents a suggestive 

 assemblage of conditions favorable to chem- 

 ical synthesis, and that these deserve a crit- 

 ical attention which the limits of this paper 

 forbid us to try to pursue into fuller detail. 

 It is clear that under these conditions 

 evaporation was permitted to develop the 

 greatest variety of concentrative effects 

 which can well be assigned to it, and that 

 at least some facilities were offered for the 

 perpetuation and modification of these con- 

 centrations when once established. It is 

 obvious that in the soil there might have 

 been any degree of exposure of the reacting 

 substances to light within very small dif- 

 ferences of depth, and that there was easy 

 intercommunication and commingling of 

 the different products of such photosyn- 

 thesis by means of capillary circulation. 

 It is obvious that in the soils there might 

 have been found the full range of capillary 

 dimensions from coarse tubes and pores 

 down to the limits of sub-capillarity with 

 the full gamut of condensation-effects as- 

 signable to these. The same may be said 

 of all catalytic effects referable to the rela- 

 tions of the solids and solutions concen- 

 trated in the soils. 



An important class of chemical reactions 

 observed in the matured plant of to-day 

 takes place within the organism without 

 much obvious addition or loss of material, 

 apparently an internal readjustment of 



matter under its own stimulus. This is 

 familiarly seen in the maturing of seeds 

 after they have been separated from all 

 connection with the plant circulation, in 

 which little external change beyond some 

 possible loss of moisture is observable. In 

 many cases, germination will not take place 

 at once; a period of internal organization 

 or ripening must intervene. This thus rep- 

 resents a last stage of preparation for self- 

 propagation, or, in other words, the last 

 stage of an advanced phase of organic syn- 

 thesis. It may not accord with conven- 

 tional usage to call this self -catalytic action, 

 but in some way it seems to be due to stim- 

 ulus which the partially organized ma- 

 terials exert on one another and by which 

 they thereby push farther forward the syn- 

 thetic process. The prevalence of this in- 

 ternal action in the last stage of the organic 

 cycle suggests that analogous action may 

 occur far back in the synthetic series, and 

 that much of the more complex part of the 

 cycle may perhaps be accomplished by such 

 action, conditioned like it on the confine- 

 ment of the partially organized material in 

 a cell-like cavity where it was subject to 

 accessions of the sustaining solutions and 

 to concentrations by the removal of water 

 and volatile matter. If this speculative 

 conception be warranted at all, the quasi- 

 cellular structure of the porous soil might 

 not inappropriately be conceived as serving 

 the function of a rude inorganic husk, or 

 shell, abetting by confinement and protec- 

 tion the internal synthesis of its contents. 

 If we may appeal to still other agencies 

 whose functions are as yet imperfectly un- 

 derstood, the electrolytic action of earth- 

 currents may be worthy of mention. It is 

 well known that saline waters are better 

 conductors of electricity than fresh waters 

 or dry earth, and hence it is probable that 

 the restoration of electrical equilibrium on 

 the earth 's surface after it has suffered dis- 



