INTERDUNAL PONDS AND TAMARACK SWAMPS 197 



(Fig. 228), is often found associated with it. Beyond the outer 

 edge of the sedge mat one often finds bladderwort (Fig. 64) 

 growing in- the water. As one walks over this sedge mat the 

 surface heaves up and down 

 as if one were walking on 

 rubber ice. In places where 

 the sedge mat is thin, cat- 

 tails are likely to be growing. 

 Farther back toward shore 

 where the sedge mat rests 

 on the peaty soil a number 

 of characteristic plants are 

 to be found. The orchids 

 are present, especially 

 Arethusa bulbosa (Fig. 229) 

 and the grass pink, Calapo- 

 gon pulchellus (Fig. 230). 

 The sun dew, Drosera ro- 

 tundifolia (Fig. 231) is a 

 small but striking plant. 

 The little round leaves are 

 covered with upright glan- 

 dular hairs, at the tip of 

 each of which is a drop of 

 sticky substance sparkling 

 like dew. This leaf is an 

 insect trap. When the insect _ 



FIG. 238. -Fragrant ladies -tresses, Spi- 



alightS upon it, it Sticks as ranthes Romanzoffiana (details in small fig- 

 it would to fly paper. The ures -) Drawin s b y L- N. Johnson, 

 leaf then closes, the tips of the hairs are pressed against the 

 body, the animal is digested, and the plant feeds upon the 

 absorbed organic material. The other plants of this same associa- 

 tion are the swamp milkweed, known by its .milky juice and 

 flowers like the other milkweeds, the marsh bellflower, tickseed, 

 Coreopsis grandiflora (Fig. 232), cottony grass (Fig. 233), swamp 



