206 FRESH-WATER BIOLOGY 



the others. Further analysis discloses the reason for this. The 

 suspended plants were found to contain relatively twice as much 

 starch as the others. This means that the suspended plants, though 

 dwarfed to one-half the normal size, still contained the same weight 

 of starch that they would have contained if allowed to grow as the 

 others did in the soil. Evidently the retarded growth cannot be 

 because of any scarcity of starch. Since this process of starch- 

 making is one of the very vital processes of the plant it is im- 

 portant to know that being artificially anchored does not disturb 

 this fundamental function of the plant. However, as a conse- 

 quence of this fact, it is evident that the suspended plants must 

 soon become overcrowded with stored starch and this result in 

 itself may be a reason for further disturbance of vital processes 

 with eventually fatal consequences. 



The proteid content of the suspended plants was found to be 

 smaller, suggesting that sufficient supply of nitrogenous food was 

 not available for them. This shows that the suspended plants 

 must have very soon fallen into an abnormal condition in which 

 the two very fundamental functions of starch-making and of pro- 

 teid synthesis were not properly balanced. 



The analysis showed further that the suspended plants contained 

 a relatively smaller proportion of mineral matter, which of course 

 indicates that they were unable to secure and use as much mineral 

 food as they needed. The elements most deficient in the suspended 

 plants were potassium and phosphorus, two of the most essen- 

 tial substances which are no doubt much concerned with the man- 

 ufacture of food materials. 



So far, then, as present knowledge is concerned we can say that 

 the plants are dependent upon the soil for a sufficient supply of 

 certain substances, especially nitrogen, potash, and phosphorus. 

 When the plants are compelled to take all their nourishment from 

 the water an abnormal condition soon arises by reason of a dis- 

 proportion between proteid synthesis and starch manufacture which 

 is manifested by a retarded growth and final death. 



That such statements are not conclusively proven must not be 

 overlooked and just why they cannot be regarded as beyond doubt 

 would be tedious to explain here. 



