POTAMOGETONS IN RELATION TO POND CULTURE. 265 



plants which have been ujirooted appeared always to possess a comparatively simple, 

 erect stem which developed from a winter bud withotit the ramifications of rootstock 

 which are characteristic of other species of Potamogeton not grasslike in habit. 



rOT.WIOGETON OBTUSIFOLIUS. 



This species is apparently an important aquatic forage plant, for its delicate leaves 

 show abundant evidence of larval depredations throughout the growing season. It is 

 somewhat grasslike, yet less stiff and harsh than the preceding species. It is a rare 

 Potamogeton in the ilora and has been observed in one place only, Spencer Lake, where 

 it is found in a muddy substratum in shallow waters of more or less swiftness. The 

 plant has a bushy habit of growth, branching widely toward the summit, a habit which 

 tends to produce dense patches of these plants. At one jilace in the station it grows in 

 such dense masses as to choke up the mouth of a small stream entering the lake. 



The plants are late in appearing among the other aquatic forms in the spring, 

 lagging behind P. zosterifolius a month or more. The bushy habit of the plant begins 

 to show itself early in- the summer, when branches arising near the base of the plant 

 ramify toward the top until the characteristic bushy habit is attained. Fruit is pro- 

 duced abundantly, but doubtless an equally important structure in the reproduction and 

 distribution of the species is to be found in the large winter buds. These appear on the 

 much-branched stems in great numbers and differ in no essential respect from those of 

 P. zosterifolius except that they are much less stiff. As in the above-mentioned species, 

 they fall away from the parent plant when mature and sink to the bottom. Like 

 P. zosterifolius, too, there is characteristic simplicity in the underground system. The 

 mature plants which have been collected show no tendency to produce ramifications in 

 the substratum, nor any indication of a perennial habit, but the plants become readily 

 propagated vegetatively by means of winter buds or hibemacula. 



POTAMOGETON FILIFORMIS. 



A habit sketch of this plant is shown in figure 36. Morong (1893) states that this 

 is a rare species in the United States. One collection only was obtained. The specimens 

 were found early in July near Canoga on Lake Cayuga, where the plant flourished in 

 shallow water and among calcareous rocks along the shore. The plants were short and 

 bushy in habit and bore abundant fruit. In all cases the erect axes developed from a 

 tuberous rootstock which, judging from the numerous erect shoots that grew therefrom, 

 is the common method of vegetative propagation in this species. The tubers (fig. 37) 

 occurred in series of 3 to 5 on the rootstock. Although no opportunity was afforded 

 for studying this plant during the successive seasons, it is deemed worth while to 

 record the observations of one collection of plants, since this species of Potamogeton 

 is unique in its habitat and promising in the possibility of seed and tuber production. 



POTAMOGETON PECTINATUS. 



This species possesses many important characteristics which recommend it to the 

 culturist of aquatic plants. It is one of the most abundant and widespread of the 

 Potamogetons. P. pectinatus is regularly found in quiet waters, though it has a variable 

 habitat in other respects, occurring in a substratum that is sandy or muddy and in waters 



