A III erica II Fisheries Society. 93 



of the species will luaiiiliiiii a yrowtli on any of tliese soils and 

 continue to reproduce each season, hut it is onlv on the good 

 loamy soil that the dense aquatic meadows occTir, 



From a study of such meadows, some of the l'uiicti(»ns hith- 

 erto assigned to aquatic plants have been estaljlishcd, such as 

 protection to animals seeking refuge, a base of attachment for 

 the growth of Algae, and even as direct food for some animals. 

 It is in protected caves little disturbed by wave action that such 

 meadows occur, and the aeration of the water is an ini poet ant 

 duty of the plants here. During the daytime all green plants 

 give off oxygen as a waste of product in the manufacture of 

 starch, and an excellent idea of what this amounts to mav \)v 

 obtained by oljserving the almost constant stream of bubbles 

 that rise from the plants on a bright day. Biit perhaps the 

 most imiiortant ])art played l)y the larger aquatic i)lants is the 

 one only recently established, that of contril)uting to the 

 plankton food supi)ly. One author has recently state(| that 

 there is a direct relation Ix'tween the quantity of ])lankton and 

 the proportion of nitrates in the water. During each season by 

 the changing winds and currents a large amount of plant debris 

 is carried out into the lake froin the aquatic meadows, where 

 during the period of its slow oxidation, it is available as food 

 for the animal plankton and when oxidized, the mineral salts 

 taken from the soil are contributed to the water to be used by 

 the plant plankton in organizing more animal food. It is thus 

 apparent that in the economy of nature, water plants have tlie 

 same part to plav with respect to organisms of a higher order, 

 as the terrestrial plants; that is, they are the organizers of inor- 

 ganic matter for the Ijenefit of the higher organisms dependent 

 upon their activity. 



It is quite probable that the waters poor in ])lankt(in will l)e 

 found to have a small growth of the attached aquatics. Certain 

 it is, at least, that in any explanation to account for a scarcitv 

 of plankton in a given water, the relative abundance of tlie 

 aquatic plants would necessarily be considered. 



Some s])ecies are much more dependent u])on the soil than 

 others. Chara and ^lyrinphyllum are not as dependent as 

 A'allisncria and Potamogeton perfoliatus. The two latter plants 

 would be excellent to plant in fish' ponds, because they are so 



