THE LARGER AQUATIC \'EGETATIOX 209 



actual contribution of organic matter to the food supply of the 

 animal Ufe. There is no doubt but that in a body of water like 

 Lake Erie this contribution of organic matter made from soil and 

 air constituents that would otherwise remain unused could be meas- 

 ured in tons even in a single growing season. 



In the marshes and shallow places immense quantities of plant 

 debris are constantly occurring and with changing wind these 

 masses of organic matter are carried far out into the lake, where, 

 during the period of slow decay, they furnish food to hosts of small 

 animals and in the decay yield valuable mineral salts, thus enrich- 

 ing the water to the advantage of the free swimming forms. 



IMPORTANT REFERENCES ON HIGHER AQUATIC PLANTS 



Britton, N. L., and Brown, A. 1896-98. Illustrated Flora of the Northern 

 United States, Canada, and the British Possessions. 3 v. New York. 



CoNARD, H. S. 1905. The Waterlilies: a Monograph of the Genus Nym- 

 phaea. Carnegie Inst, of Wash., Pub. No. 4. 



Coulter, J. M., Barnes, C R., and Cowles, H. C. 191 i. Textbook of 

 Botany. Vol. 2. New York. 



Engler, A. 1900+. Das Pfianzenreich. Leipzig. 



Engler, A., and Prantl, K. 1887+. (See list in Chapter VL) 



Gluck, Hugo. 1905-06. Biologische und morphologische Untersuchungen 

 iiber Wasser und Sumpfgewachse. 2 v. Jena. 



Kerner, a., and Oliver, F. W. 1895. The Natural History of Plants, 

 their Forms, Growth, Reproduction and Distribution. 2 v. in 4 

 New York. 



Morong, Thomas. 1886. Studies in the Typhaceae. Bull. Torrey Bot. 

 Club, 15: 1-8, 73-81. 

 1892-93. The Naiadaceae of North America. Mem. Torrey Bot. Club, 

 V. 4, No. 2; 65 pp., 55 pi. 



Pieters, a. J. 1894. The Plants of Lake St. Clair. Bull. Mich. Fish Com., 

 No. 2; 10 pp. Map. 

 1901. The Plants of Western Lake Erie with Observations on their Distri- 

 bution. Bull. U. S. Fish Comm., 21: 57-79, 10 pi. 



Pond, R. H. 1905. The Biological Relation of Aquatic Plants to the Sub- 

 stratum. Rept. U. S. Com. of Fish and Fisheries 1003: 483-526. 



Warming, J. E. B. 1909. Oecology of Plants; an Introduction to the 

 Study of Plant Communities. Oxford. 



