POTAMOGETONS IN RELATION TO POND CULTURE. 259 



Substratum, the aiitlior showed that rooted aquatics depend on the soil substratum for the supply of 

 nitrates. In conducting tlie experiments various aquatic plants were used, among which were P. per- 

 folialus and P. obtusifoUus. It was found that both of these plants are dependent on the soil substratum 

 for optimum growth, though the cuttings which were employed behaved differently in manner of growth : 

 P. pcrfoliatus showed an increase of growth through the development of new rhizomes; P. obtusifoUus 

 manifested it in a continuation of the branches already present. The behavior of P. perfoliatus is in 

 accord with the observations of Sauvageau in his experiments on the propagation of Potamogetons by 

 fragments of stems. 



The second paper of the author, The Larger Aquatic Vegetation, to appear in Ward 's American 

 Fresh-water Biology, supplements the work of the first by additional observations, discussions, and 

 generalizations. From his observations on the substratum of the larger aquatics it appears that they 

 may be found growing on gravelly, sandy, or loamy soil, the loamy soil supporting the greatest variety 

 of species. Direct experiments on this point, with the natural conditions reproduced as nearly as 

 possible, bear out this observation. The author states, moreover, that the character of the soil is so 

 important a factor that it is possible to predict the nature of the bottom from the species that are found 

 growing in it. For example, "Among the islands of western Lake Erie Poiamogeton hetcrophyllus is 

 common on the reefs and pebbly shores, but it is not noticeable in the coves where a good soil sub- 

 stratum exists, and so prominent is it in the former places that its presence may be considered char- 

 acteristic of the flora. " 



JEPSON, 1905. 



In a popular article in the Sunset Magazine for February, 1905, Prof. W. L. Jepson has set forth the 

 possibilities of the marshes as a feeding ground for ducks. He has taken as a concrete illustration the 

 Suisun Marshes in California, marshes which abound in the fennel-leaved pondweed, P. pcctinalus, 

 and which afford natural feeding grounds for the various kinds of wild ducks, more particularly the 

 canvasbacks. The canvasback and the broadbill, both diving ducks which visit these marshes, devour 

 greedily the tubers that are developed in abundance on the rootstocks and upper portions of the stems 

 of this Potamogeton in the autumn. It is claimed that these tubers give the fine nutty flavor to the 

 canvasback at this season of the year. Other ducks, nondiving species, feed on the tender rootstocks 

 and leafy stems which are brought to the siuface in the feeding operations. 



ASCHERSOX .AND GrAEBNER, 1907. 



Ascherson and Graebner have published the last important monograph on the group, the Potamo- 

 getonaceae, in Das Pflanzenreich. In this work the whole number of the described species has reached 

 87. Of these North America has 38, 14 of which are exclusively American. The numerous forms and 

 varieties that are listed, though some common ones are omitted, illustrate how difficult the problem 

 of classifying the Potamogetons still remains. In addition to the literature on classification the authors 

 have assembled much important data on the anatomy and morphology of the group from foreign sources 

 not generally accessible. Under the caption, Uberwintenmgsforraen und Vegetative Vermehrung bei 

 Potamogeton, the following propagative structures are figured: The slender, spicular bur of P. crispus; 

 the large denticulate bur of P. crispus; the tuberous rhizome of P. lucens; the tubers of P. pectinatus; 

 and the winter bud of P. obtusifoUus. All except the first are reproductions of Irmisch's celebrated 

 monograph. 



McAtee, 1911. 



In a bulletin of the Biological Survey entitled Three Important Wild Duck Foods, Mr. McAtee has 

 assembled for Government publication important data regarding these foods, in the hope that they may 

 become more widely known and propagated for the preservation of wild ducks. Analyses of the food 

 content in the stomachs of the more important species of tlie game ducks show that the pondweeds, the 

 Potamogetons, are a favorite plant food. The ducks which apparently show a special fondness for it 

 are the canvasback, the redhead, the scaup, and others, the first of which takes a very large proportion 

 of the Potamogeton, the amount being nearly 50 per cent of the food eaten. 



The best known duck food among the Potamogetons is P. pectinatus, of which the seeds, the tender 

 rootstocks, and the tubers are eaten. It is general in distribution, thriving in fresh, brackish, or salt 

 water. This and other widely distributed species are figured, and suggestions on how, when, and where 

 to plant them are given. 



