TEACHERS DEPARTMENT. 
287 
and fields, I have met with scarcely any success. I should be 
glad if some of your readers who have accomplished anything in 
this line would make some statement of their work in your maga¬ 
zine, and tell how they do it. 
Very truly, 
W. J. Beal. 
THE TEACHERS DEPARTMENT. 
Edited by Professor C. Stuart Gager. 
The Biological Relation of Aquatic Plants to the 
Substratum. 
In the biological survey of the Great Lakes, the United States 
Fish Commission had for one of its problems to ascertain the 
factors determining the quantity of food fish that the lakes can 
support. On account of the interrelationships of different forms 
of life, it became necessary to study, besides the fishes themselves, 
the plants and other animals of the lakes upon which the fishes 
either directly or indirectly depend. In the report of the Fish 
Commission for 1903, under the above caption, Pond gives the re¬ 
sults of a series of instructive experiments. 
We have different opinions and different experimental data on 
the question as to whether rooted aquatic plants absorb nourish¬ 
ment throughout their entire surface, the roots serving merely 
as holdfasts, or whether absorption takes place through the roots 
accompanied by currents through the tracheae, and an exudation 
analogous to transpiration. 
Among other plants, Vallisneria spiralis, Ranunculus aquatilis 
trichophyllus, Elodea canadensis, Myriophyllum spicatum, Pota¬ 
mo getum obtusifolius and P. perfoliatus were studied. The fol¬ 
lowing are some of the author’s conclusions: 
The roots of these plants are organs of absorption as well as of 
attachment. There is an upward current in these plants, from 
roots to stem and leaves. Many of the plants rooting in soil 
develop root hairs, and the presence of these structures is the rule 
rather than the exception. Ceratophyllum and some other float¬ 
ing plants are able to absorb their nutrient salts directly from the 
