208 TYPES OF BRITISH PLANTS 
of the capture. You may remember that nitrogen com- 
pounds are necessary to the formation of protoplasm. 
Now, some soils are not very rich in these, but animal. 
substances are. Marshy soils are specially poor, and we 
shall find that almost all our examples of marsh plants 
live either in water or in bogs. Another curious point 
is that it is quite possible to overfeed a Sundew, for 
instance, with animal food, as you will probably find 
out if you ever keep a Sundew and feed it with flies, 
and the wretched plant dies painfully of indigestion ! 
As an example of the simple trap, let us take the 
Bladderworts, the pale flowers of which you may see 
lifted up above the surface of moorland pools, its few 
leaves floating level with 
the top, and its roots 
At fs straying vaguely about 
“ips in the water. On these 
IN roots are tiny bladders, 
measuring abouta quarter 
of an inch in diameter, 
. which you should ex- 
amine under your magni- 
fying-elass. You will find 
= 
that at one of the lower 
corners there is a fringe 
of stiff projecting bristles, . 
leading to a small trap- 
- door in the centre of the 
fringe, which opens only 
inward. An inquisitive 
water-flea, voyaging pos- 
sibly in search of food, 
BLADDERWORT. or perhaps escaping from 
