138 MOUNTAIN AND MOORLAND 



of the tarn, and best of all is the Bladderwort (Utricu- 

 laria\ with beautiful golden flowers which are lifted 

 erect above the surface about midsummer. It belongs 

 to the same family as the Buttercup (Pinguicula) of 

 the bogs, but it has no true roots and floats freely in 

 the water. The long, root-like stems bear delicate, 

 needle-shaped leaves and here and there little bladders. 

 These seem to be transformed tips of leaves, and they 

 serve as traps for minute larval Water Snails and 

 insects and for equally small Crustaceans, popularly 

 called Water Fleas, such as Daphnia, Cyclops, and 

 Cypris. The narrow entrance to the trap is guarded 

 by branched hairlike filaments, which perhaps ward 

 off larger intruders. They secrete a little mucilage 

 which is appetising to the Water Fleas. These push 

 their way in and a valvelike door yields before them. 

 As they get inside, however, the door shuts behind 

 them, and it cannot be opened from within. Thus the 

 visitors are imprisoned and sooner or later die. After 

 they are dead and decayed the Bladderwort absorbs 

 the soluble remains by means of delicate fourfold 

 hairs. 



Llike Water Milfoil (Myriophyllum) and some of 

 the Pondweeds (e.g., Potamogeton crispus), the 

 Bladderwort forms special winter buds, rich in 

 reserve material. They are formed in autumn, close- 

 packed clusters of bright green leaves, and they fall 

 off the floating stem which is dying away and sink 

 into the mud. There they spend the winter resting, 

 but when spring comes they are buoyed up with gas 

 bubbles and rise to the surface to form the long 

 floating stem. Thus we see how the Bladderwort, 

 submerged all but its flower-stalk, ekes out a liveli- 



