26o BULLETIN OF THE BUREAU OF FISHERIES. 



MiCKLE, 1912. 



A Canadian bulletin, The Possibilities of Northern Ontario as a Breeding Ground for Ducks, by 

 G. R. Mickle, is an investigation of the shoal waters of that Province with a view to their utilization 

 for the propagation of wild game. In the preliminary survey the approximate amount of shoal waters 

 is estimated to be 2,800,000 acres, on which various edible water plants grow. But it is hoped that 

 the natural supply may be augmented considerably by transplanting such of the larger aquatics as will 

 contribute especially to the food of wild ducks. Among the valuable water plants suitable for trans- 

 planting, the author names several species of Potamogeton, P. natatis, because of its abundant seed 

 habit, P. perfoliatus and P. crispus because of their edible leaves. 



Mickle and Thompson, 1913. 



A second Canadian bulletin by G. R. Mickle, written in collaboration with R. B. Thompson, 

 supplements the work already done in this line. A table giving the estimated percentages of the 

 various constituents of duck food shows that both P. heterophyllus and P. perfoliatus form an im- 

 portant food constituent in the diet of wild ducks. 



It will be seen from the foregoing resume of the literature on the genus Potamoge- 

 ton, that an important extension of the subject is in the field of biologic research, an 

 aspect of the study which regards also the economic significance of the group. It is 

 apparent, too, that this field of research concerns itself primarily with the propagation 

 of Potamogeton by such structures as tend readily and effectually to distribute the 

 group, viz, by burs, tubers, rootstocks, and winter buds. These have been described 

 generally in Europe and in America, and one may consider their production a natural 



phenomenon. 



SPECIES OF POTAMOGETON INVESTIGATED. 



The species which are included in this investigation have been selected from the more 

 or less common forms growing in the lakes and ponds at Ithaca, N. Y., and vicinity 

 (Spencer and North Fairhaven). And these species have been chosen because they 

 offer variety in habitat and in methods of propagation, and because they serve an 

 important role in the economic relations of aquatic life, affording food, shelter, and 

 support to many forms of animals which exist among them. The list of species follows : 



P. americanus C. and S. 



P. amplifolius Tuckerm. 



P. hekro phyllns forma ierrhtris Schlechtd. 



P. perfoliatus L. 



P. crispus L. 



P. zosterifolius Schumacher. 

 P. obtusifolius M. and K. 

 P.filiformis Pers. 

 P. pectinatus L. 

 P. Robbinsti Oakes. 



These Potamogetons were studied from September, 191 2, to June 1914, in their 

 natural habitats and in aquaria. Entire plants were thus observed throughout the 

 period of development of those structures which are valuable in the vegetative propa- 

 gation of the species. From time to time collections were made of entire plants with 

 their subterranean systems intact. In shallow waters the plants were uprooted by 

 hand, but in the deeper waters they were obtained by means of a rake or a grapple 

 thrown over the side or the stern of a rowboat. No collections were made in mid- 

 winter, i. e., from the latter part of December to the middle of February, when the 

 frozen condition of the lakes and streams rendered it impracticable. P. crispus is an 

 exception, since it was collected from spring pools at all times of the year. 



These studies have afforded an opportunity to obser\-e the animals that are inti- 

 mately associated with the Potamogetons. vSuch have been noted, especially those 

 forms which depend upon these plants for food, support, or shelter. 



