40 Chapters in Modern Botany CHAP. 



Aldrovanda. Allied to Dionaea, and with a some- 

 what similar leaf, is a water fly-trap {Aldrovanda vesicu- 

 losa), which lives in clear well-sunned ponds in south and 

 central Europe, and also occurs in Australia and India. 

 Like the common bladderwort, Aldrovanda has a thin root- 

 less floating stem, which bears whorls of modified leaves. 

 It dies away at one end as it grows at the other, and is 

 reduced in autumn to a concentrated tuft, which sinks for 

 the winter to the muddy bottom of the pond, thence to rise 

 again in summer after it has exhausted its stores of starch 

 and has become buoyant with gas. The little leaves have 

 a spathulate stalk and a folding two-lobed blade with teeth 

 round the edges. Although in figures of the plant the 

 leaves are commonly represented as open, like those of 

 Dionaea, it is said that their lobes really open only about 

 as much as the valves of a living mussel, and are thus the 

 better fitted for capturing small animals. The surface bears 

 numerous sensitive jointed hairs and colourless stalked 

 glands, and the leaf closes on water-fleas, larvae of insects, 

 and even diatoms, very much after the fashion of Dionaea. 

 Darwin believed that the glands secrete a digestive fluid, 

 and that small four-lobed hairs situated on the outer thinner 

 parts of the leaf absorb decaying animal matter. Goebel 

 is inclined to think that these four-lobed hairs secrete some 

 slimy substance, perhaps attractive to small animals. 



Sundews and Birdlime Traps. It is said that Portu- 

 guese peasants use as a substitute for fly-paper the viscid 

 leaves of Drosophyllum lusitanicum, a common plant in 

 dry, sandy, or rocky places in Portugal and Morocco, and 

 hence, it is worth noting, with a much better developed 

 root system than its marsh-loving allies. It grows eight 

 or ten inches high, and has long narrow strap-like leaves 

 (which are interesting as being rolled up in the bud like 

 those of ferns, but backwards instead of forwards), beset 



