262 BULLETIN OF THE BUREAU OF FISHERIES. 



extensive ramification of underground stems, richly provisioned with starch, remains 

 more or less intact during the winter, carrying at alternate nodes undeveloped shoots 

 which quickly establish new extensions of the plant in the spring. Another means of 

 vegetative propagation is found in the detached tips of branches which, after separation 

 from the decaying parent stem in the fall or spring, sink to the bottom and become new 

 centers of growth. New shoots also develop at the nodes of decaying stems and, on 

 separation, sink to the bottom and take root as in the case of detached tips and stems. 

 Besides these vegetative means of growth this Potamogeton produces an abundance of 

 seeds. 



POTAMOGETON HETEROPHYLLUS. 



Various forms of this species occur throughout almost all of North America except 

 the extreme north. One of the numerous forms, forma terrcsfris Schlectd., is repre- 

 sented in this investigation and all data herein recorded pertain to this plant. It is a 

 so-called land form of Potamogeton and briefly characterized in Gray, seventh edition, 

 as "freely creeping in exsiccated places, producing numerous branches which bear tufts 

 of oblong or oval coriaceous leaves but no fruit." This plant, which grows in the open 

 air after being left entirely uncovered by water, has been observed in two places along 

 the shores of I^ake Cayuga — one in a railroad pool 2 miles east of Ludlowville and the 

 other on a sandbar at Myers Point. In each of these places it is interesting to note 

 that gradations in habit accompany the varying changes in habitat. The railroad 

 pool is a particularly favorable spot for the growth of this Potamogeton. It is an 

 artificial pond which has been developed by building a railroad embankment near the 

 foot of the bluff bordering the lake. In consequence, a long, trough-like depression 

 exists between the bluff on one side and the railroad embankment on the other, with 

 water from the lake seeping through and maintaining itself at about the level of the 

 lake. It is a situation especially favorable to the growth of this plant, because the 

 annual withdrawal of the water is gradual, following the natural lowering of the lake level 

 during the summer months. The bottom of the pool is covered with black mud, largely 

 marl in composition, a foot or more in thickness, over which water may rise to the height 

 of 12 to 16 inches. During high-water level in the spring, this Potamogeton grows 

 submerged in the pond with its tuberous rootstalks anchored in the mud (fig. 8). Upon 

 the withdrawal of the water, following the lowering of the lake level in the summer, 

 drought conditions prevail, and then the submerged leafy stems give place to the land 

 forms. Upon the approach of drought conditions the previously submerged leaves die 

 and from the main rootstock or from those arising from the axils of the lower leaves 

 (upper in some cases, Bennett, 1880) runners extend horizontally to a depth of 2 to 6 

 inches below the surface of the mud. From the fertile nodes of these runners erect 

 axes arise, bearing tufts or rosettes of leaves which cover the ground in great numbers 

 and compete with mosses and small forms of sedges, carpeting the surface of the mud. 

 The leaves of the rosette (fig. 12) are unlike the elongated, membranous, submerged ones. 

 They are more rounded in form and coriaceous in texture, and by the presence of sto- 

 mates on the upper surface of the lamina, they are enabled to function as ordinary 

 leaves. 



