Shore Plants 321 



lakes, at a depth of 25 feet more or less, and within the 

 range of effective light. Associated with these, but 

 usually on the shoreward side, are beds of pondweeds. 

 Often there are bare wave-swept shores behind these 

 beds with no sign of aquatic vegetation that one can 

 see from the shore. 



Depth of water determines the adjustment of aquatic 

 seed plants in three principal categories: 



1. Emergent aquatics. These occupy the shallow 

 water, standing erect in it with their tops in the air, 

 and are most like land plants. They are by far the 

 most numerous in species. 



2. Surface aquatics. These grow in deeper water, 

 at the front of (and oftentimes commingling with) the 

 preceding. The larger ones, such as the water lilies 

 are rooted in the mud of the bottom, and bear great 

 leaves that float upon the surface. The smaller ones 

 such as the duckweeds (see figs. 61 and 62, p. 149) are 

 free-floating. 



3. Submerged aquatics. These form the outermost 

 belt or zone of herbage. They are most truly aquatic 

 in habits. Except for such forms as dwell in quiet 

 waters, they are rooted to the bottom. Depth varies 

 considerably within this zone. It extends from the 

 outer limits of the preceding (hardly more than five 



Fig. 189. 



A. Branches of four submerged water plants : (i) Philotria, (2) Cerato 

 phyllum, (3) Ranunculus, (4) Nais. 



B. Emergent aquatics, including a clump of arrow arum; two of the 

 pendulous club-shaped fruit-clusters are seen at (5) dipping into the water. 



C. Zonal arrangement of the plants of the shore-line. The background 

 zone is cat-tail flag (Typha). Next comes a zone of pickerel- weed (Ponte- 

 deria) in full flower. Next, a zone of water lilies and such other aquatics 

 with floating leaves as are shown in D and E. In the foreground is a zone of 

 submerged plants— a mixture of such forms as are shown in A above. 



D. A closer view: Lemna, free-floating and Marsilia with four parted 

 floating leaves, and Ranunculus, in tufted sprays, submerged. 



E. The floating leaves and emergent flower spikes of a pondweed, 

 Potamogeton. (Photo by L. S. Hawkins.) 



