114 A. H. Graves, 



Not only the evident carefulness with which he has conducted 

 his experiments, but also the variety of species and number of 

 specimens used, joined with his very positive results, should put at 

 rest all doubt as to the importance of the absorptive role of the 

 roots of submerged plants. 



On the other hand, Pond's experiments fail to show conclusively 

 whether or not water and dissolved salts are absorbed by the part 

 of the plant above the soil — a condition which is indicated by the 

 reduction of the xylem area of the root. 



Too much emphasis, therefore, must not be laid upon the ab- 

 sorbing capacity of the root, as is shown by the following con- 

 .siderations : — 1. the absence of transpiration as we are acquainted 

 with it in land plants; 2. the probable absorption by the parts of 

 the plant above the soil of nutrient solutions from the surrounding 

 water; 3. connected with these two conditions a reduction of the 

 xylem area to a few tracheae of rudimentary nature; and 4, the 

 total lack of branches and the slenderness of the roots. 



In brief, the absorption carried on by the roots of submerged plants 

 and the importance of this function in the economy of the plant is 

 much greater than is implied by Schenck, as the experiments of 

 Pond demonstrate; but, on account of the peculiar environmental 

 conditions of submerged plants, it can never equal in importance the 

 absorption of the roots of land plants. 



