THE BUTTERWORT FAMILY 97 



whole surtf>ce. the epidermis being very thin. Different salts being 

 generally c issolved in water, the plants obtain their mineral food 

 from the \iater they absorb. This being so, they require no 

 special organs of absorption, and roots are dispensed with. 

 Therefore the Bladderwort cannot exist in running water, but 

 only in pools and ponds with stagnant Avater. 



2. Absorption of Carbonic Acid Gas. — The Bladderwort is 

 green; which shows that it requires carbon dioxide to form starch 

 for its growth. This gas is found in water also, though in very 

 small quantities. To get a sutticient supply of it, the plant has 

 to increase its surface enormously by dividing the leaves into 

 hundreds of parts. Take a potato and cut it into many thin 

 slices: you will see how the surface of the piece is thus greatly 

 increased. The greater the surface of the leaves, the more the 

 area available for absorbing food. The leaves, thus split into 

 numerous thread-like segments hanging down in the water, look 

 like roots (fig. 93). 



The air absorbed by the leaves is collected in intercellular 

 spaces which form inflated bags at the base of the branches. 

 These help to diminish the weight of the plant and keep it float- 

 ing near the surface of the water. 



8. Reproduction. — In order to form seeds the plant throws 

 up little stalks above the level of the water, on which two to 

 four yellow spurred, labiate flowers are produced (fig. 93, i). 



AVhen a pool in which Bladderworts grow dries up, they die. 

 Before dying, they speedily make preparations to propagate their 

 kind by producing flowers and seeds. But they can do it in 

 another way also: the tips of the branches detach themselves from 

 the parent plant, the leaves folding over the terminal bud: they 

 then sink into the mud to rest there during the dry season, and 

 sprout when the pool is filled again with water. 



4. A Carnivorous Plant. — But the plant leads an extraordi- 

 nary life not only in so far as it lives in water, but also because 

 it feeds on animal substances. It is a carnivorous plant. To 

 oatch its prey it is provided with curious traps, Avhicli we shall 

 now examine. If the ordinary Utricularia, which has yellow 

 flowers and floats in quiet waters, cannot be obtained, the 



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