20 LIVING PLANTS 



the power of locomotion. All of the cells con- 

 tained chlorophyll and shared in the work of 

 food formation, and since more or less of the 

 surface of each cell was bathed by the fluid in 

 which it lived, all absorbed the mineral salts 

 in solution in the surrounding medium, and 

 all of the cells participated in the reproductive 

 processes. 



It will not be profitable here to follow the 

 direction or possibilities of morphological dif- 

 ferentiation into detail, except to say that the 

 organism soon found it more economical to 

 be attached to a fixed point rather than to 

 float at random or swim through the water 

 which contained the mineral salts in equal 

 diffusion, and in which the necessary intensity 

 of light bore a direct relation to the distance 

 from the surface. Then in consequence of this 

 newly acquired habit of fixation, and the re- 

 cession of the water from the substratum occu- 

 pied, some distinct and important physiolog- 

 ical changes ensued to meet the new condi- 

 tions attendant upon the nutritive processes. 

 The sunlight impinging upon the portion of 

 Chlorophyll the plant containing chlorophyll no longer 

 and sunlight came filtering down through layers of water 

 of varying depth, but beat upon it from all 

 points in an arc of one hundred and eighty de- 

 grees. The greater amount of energy thus 

 available to the aerial shoot could only be 



