VI The Web of Life 103 



nutates in sweeping circles, as if seeking about for some 

 plant on which to cling. If this be not found, the stem at 

 length lies prostrate on the ground, and after a strange 

 dormant existence for a month or so longer, dies. But if 

 some plant be near at hand, the dodder stem slings itself 

 around it after the manner of a twining plant. As soon as 

 its stem has embraced that of its bearer — let us say a nettle 

 or hop — it gives off attaching papillae which penetrate the 

 rind and bud off numerous little rootlets. These come into 

 close connection Avith the bast portion of the hop or nettle 

 stem, and thence absorb nutritive materials. Now, in 

 all plants the vessels of the bast form the channels 

 by which the complex organic substances manufactured in 

 the leaves pass towards the root. Such are the spoils 

 which the leafless dodder, unable to manufacture organic 

 stuffs for itself, absorbs from its host. After suitable 

 attachment has been effected the stem continues its twining 

 growth with increased vigour, the basal part dies away and 

 all connection with the soil is lost, and eventually the wan 

 parasite bursts into flower. 



Root-Parasites. — In some well-shaded part of the wood 

 we may find a large patch of the cow-wheat {Mela7npyrttin\ 

 a delicate plant with a pale yellow flower, akin to toadflax 

 and snapdragon. If we dig it up very carefully along with 

 the plants growing near, we may be able to see that its 

 roots are at intervals tightly bound to those of its neighbours. 

 The connection is a vital one, and effected by peculiarly 

 modified discs which grow round the roots of other plants 

 and send suckers into them. This is a clear case of root- 

 parasitism, but it is difiicult to tell how much it amounts to, 

 for the cow-wheat has also independent roots which absorb 

 water, salts, and probably decaying vegetable matter from 

 the soil, and it also is a green plant. If this habit were 

 peculiar to the cow-wheat we should not be inclined to attach 



