90 Tlnriij-First Aiiuuitl Mrrfing 



the lake;, and the sources of reueAval of this organic matter, are 

 manifestly important. It has long been known that water plants 

 contain several essential food elements in greater proportion than 

 the water, and we may say that aquatic plants concentrate with- 

 in themselves nitrogen, potash, phosphoric acid. In the case of 

 the plankton these elements must come from the water and then 

 the plants die and are returned to solution. However, with the 

 larger attached plants, we have another possibility, that is, they 

 may take their mineral food from the suljstratum, and if they 

 do, we liave in them, agents active in the transfer of mineral 

 food from the soil to the Avater. On the other hand, if the at- 

 tached plants do not absorlj nourishment from the soil, they 

 must take it from the water, and their iniiuence in this case 

 would l)e to withhold during all the growing season, matter that 

 would otlierwise be available to the plant plankton. 



The statement is common in all our text books of l^otany, 

 e\x'n those pu))lished during the present year, that aquatic jdants 

 derive their nourishment from the water and not from the soil, 

 tbat tlie roots are not organs of absorption as in land ])lants, but 

 only lioldfasts to anchor the ]>lant. A review of the literature of 

 tliis subject, shows that this statement is based upon argument 

 and not experimental data. The anatomy of water ])lants has 

 recei\'ed quite a little attention in the past, and many authors 

 have noted tliat the tissue systems for the condiiction of water, 

 wliich ill land plants are so well developed, are in aquatic plants 

 vci'y iMidimentary. ^Moreover, it has been observed that sub- 

 merged aquatics liave no eva])orating surface and hence there is 

 no iiecessity for an ujjward current in the plant. Again, the 

 entire surface of sul)nu'rged plants is permeable to water and 

 tile plant may easily secure its mineral food directly from the 

 surrounding water. Sueli has been the majority opinion and 

 argunienl u]> lo the ])resent time; but investigation now com-' 

 pleted though as yet unpublished, ])roves lieyond a doubt, I 

 think, that most of our eominou aquatic- plants are absolutely 

 dependent upon l)eing rooted in the soil for optimum growth, and 

 few of them indeed can sur\i\e the growing season, if denied 

 attachment to the soil. 



To consider now some of the evidence for the latter opinion. 

 Su])pos(; we construct some large boxes and build a raft around 



