SUNDEW FAMILY 



77 



Ord. XXIX. Droserace^e. — The Sundew Family 



An interesting group of herbaceous marsh plants widely 

 dispersed over the globe, but specially common in Australia. 

 They will grow on wet sand or moss, depending only for 

 water on the substratum, and their roots are accordingly small. 

 Their chlorophyll is often little developed, the whole plant being 

 reddish, and the leaves in 

 several genera covered 

 with insectivorous glan- 

 dular hairs. The Jlozvers 

 are polysymmetric and 

 usually 5-merous, the 

 sepals and petals being 

 imbricate, the stamens in 

 i — 4 whorls, the carpels 

 sometimes reduced in 

 number, with distinct 

 styles, and forming a 

 i — 5-chambered, many- 

 seeded capsule. In Dro- 

 sera, the largest genus 

 and the only one repre- 

 sented in Britain, the 

 leaves have many-point- 

 ed lobes or tentacles, 

 each ending in a gland 

 exuding a viscid fluid, 

 especially when the sun 

 is shining, so that they 

 appear as if tipped with 

 dew, whence the various 

 names of these plants. 

 These tentacles are at 

 first spreading and the 

 fluid neutral ; but on capturing a small fly, or on contact with any 

 nitrogenous substance, the fluid becomes acid and the tentacles 

 bend towards the centre of the leaf, where the fly is digested. 

 Dionka muscipula (Venus' Fly-trap), a native of Carolina, has 

 non-glandular tentacles round the margin of the leaf and a few 

 long hairs on its upper surface. When these hairs are touched by 

 an insect the two halves of the leaf close together instantaneously 

 by an electrical action, the tentacles interlocking like the teeth of 

 a gin, and an acid digestive fluid is then exuded by glands on the 



drosera rotundif6lia (Round-leaved Sundew). 



