264 BULLETIN OF THE BUREAU OF FISHERIES. 



POTAMOGETON CRISPUS. 



This species, a native of Europe, was recorded in this country by Pursh as early 

 as 1814 (Arthur Bennett, 1901). Since that time it has become established over an 

 extensive area because of the remarkable facility for multiplying itself vegetatively. 

 It is the most abundant Potamogeton in the vicinity of Ithaca, where it flourishes in 

 various habitats — in deep or shallow water, in sand or mud bottoms, and in stagnant 

 pools or flowing streams. It is singularly adaptive in each situation. It has been 

 collected with P. pectinatus growing at depths of 8 feet, in which habitat the internodes 

 are extremely elongate; it has been found in pools where the substratum is an accu- 

 mulation of debris from ash heaps and dumping grounds; and it is not uncommon in 

 the swifter parts of streams and along the lake shore in sandy situations where the 

 substratum is thrown into ripples by wave and current action. In the latter situation 

 it has always possessed short, stocky stems and a general dwarfish appearance. 



P. crispus grows the year round and spreads with great rapidity. It is propagated 

 primarily by "burs," peculiarly distinctive structures to which there is nothing quite 

 comparable in our native species. Morphologically they are branches, but in the stage 

 most frequently seen they are scarcely recognizable as such members of the plant 

 structure. They have a horny look and a reddish color. The shortened internodes 

 and thickened persistent leaf bases combine to give the characteristic bur-like appear- 

 ance (fig. 22). 



POTAMOGETON ZOSTERIFOLIUS. 



This flat, grass-like species of Potamogeton is not largely foraged upon by aquatic 

 herbivores, yet it appears in greater or less abundance in most ponds and lakes and 

 doubtless serves an important role in the economy of life by furnishing support and 

 shelter to the countless small forms which have been found upon it. 



P. zosterijolius is among the earliest of the Potamogetons to appear in the spring, as 

 well as among the first of them to disappear in the autumn. It flourishes in a sub- 

 stratum of mud in still or running waters, and while it is not adapted to possess the soil 

 so completely as P. crispus, nevertheless it has effective means of perpetuating itself. 

 Mr. A. J. Pieters (1901) remarks that this species, which he has observed growing in 

 abundance in Lake Erie, may be losing the power to prodilce seeds. Indeed, during the 

 past season few plants matured seeds in the several regions where they were observed, 

 but all developed winter buds in great abundance (fig. 33). 



Large quantities of vegetation, that is, the accumulation of the varied and abundant 

 mass that still exists in the autumn, have been hauled up to the surface for examination, 

 and it was both surprising and astonishing to see the vast number of winter buds of 

 this Potamogeton that were entangled among the stems of other plants. It suggests to 

 an extent how well this species accommodates itself to its surroundings. It never 

 forms dense patches of growth, but it often occurs with aquatic plants that form them 

 more or less densely. By virtue of its slender, grasslike habit, it occupies the interstices 

 of the more rank aquatic flora, and it occupies these spaces as simple individual plants, 

 not as erect axes of a complete and intricate subterranean system. The plants are 

 anchored to the substratum by the roots only, which develop from the winter bud, and 

 because of this loose hold in the soil they are readily pulled up. The large number of 



