THE BOOK OF NATURE STUDY 



cularia minor) has much smaller floating branches, not more 

 than three inches long, and the leaves have few bladders ; the 

 flowers are pale yellow and much smaller. This is a commoner 

 species than the other. The Intermediate Bladderwort (U. 

 intermedia) differs from these two species in the fact that the 

 bladders and leaves are borne on different branches ; it is a rarer 

 species than the other two, and does not often blossom. The 

 bladders are modified leaflets, each attached by a little stalk to 

 the submerged floating stem. At the upper end of the sac-like 

 bladder there is a small opening, around which are a number of 

 stout forked bristles (Fig. 9). The opening is closed by a valve, 



which opens inwards, and shuts like a spring 

 door against the thickened rim of the aper- 

 ture. By means of these bladders the plant 

 captures an immense number of small aquatic 

 animals. Darwin found four, five, eight, or 

 even ten, minute crustaceans in the bladders 

 he examined. What attracts these animals 

 to the bladder is not positively known ; they 

 may be seeking a hiding-place from larger 

 animals, and the bladder being transparent 

 may attract them. They push against the 

 valve, which yields at once, then as soon as 



FIG. 9. Bladderwort ,,.,,_ -, n 



(Utricuiaria\ A single the animal has entered closes again, so that 



flower and bladder on it cannot escape. The bladder is lined with 



the right CC -Q S a( } a pted for absorbing the products of 



the decaying body, but there does not appear to be any special 



digestive juice, as in the Sundew. 



It is easy to recognise the Sundew from the long bright red 

 hairs, or tentacles, on the edges of the leaves. The three species 

 may be distinguished from each other by the following characters. 

 The Round-leaved Sundew has round leaves, lying almost flat on 

 the ground ; this is the most common species. The Long-leaved 

 Sundew (Drosera anglica) has upright leaves, about six times as 

 long as they are broad, and a flowering stem which rises erect 

 from the centre of the leaves. The Intermediate Sundew may 

 be recognised by the flowering stem, which is horizontal in its 

 lower part, then erect. These plants perform movements by 



