PHYSIOLOGICAL INTEGRATION IN PLANTS. 293 



each dies if detached from the other. That though the 

 organization is so low neither part can reproduce the other 

 and survive by so doing, is probably due to the circumstance 

 that neither part contains any considerable stock of untrans- 

 formed protoplasm, out of which new tissues may be pro- 

 duced. 



Fungi and Lichens present no very significant advances 

 of integration. We will therefore pass at once to the 

 Archegoniates. In those of them which, either as single 

 fronds or strings of fronds, spread over surfaces, and which, 

 rooting themselves as they spread, do not need that each part 

 should receive aid from remote parts, there is no developed 

 vascular system serving to facilitate transfer of nutriment: 

 the parts being little differentiated there is but little integra- 

 tion. But along with assumption of the upright attitude and 

 the accompanying specializations, producing vessels for dis- 

 tributing sap and hard tissue for giving mechanical support, 

 there arises a decided physiological division of labour ; render- 

 ing the aerial part dependent on the imbedded part and the 

 imbedded part dependent on the aerial part. Here, in- 

 deed, as elsewhere, these concomitant changes are but two 

 aspects of the same change. Always the gain of power to dis- 

 charge a special function involves a loss of power to perform 

 other functions; and always, therefore, increased mutual de- 

 pendence constituting physiological integration, must keep 

 pace with that increased fitting of particular parts to particu- 

 lar duties which constitutes physiological differentiation. 



Making a great advance among the Archegoniates, this 

 physiological integration reaches its climax among Phseno- 

 gams. In them we see interdependence throughout 

 masses that are immense. Along with specialized appli- 

 ances for support and transfer, we find an exchange of aid at 

 great distances. We see roots giving the vast aerial growth 

 a hold tenacious enough to withstand violent winds, and 

 supplying water enough even during periods of drought; we 

 see a stem and branches of corresponding strength for up- 



