INSECTIVOROUS PLANTS 361 



spread over and twine around other stems ; and it is an 

 interesting fact that usually only a few turns are made 

 around a single ' host '-stem, but from these coils many 

 haustoria may be given off. In time, many bunches of 

 small flowers are formed, each flower being like a tiny 

 Convolvulus. Dodders {Cuscuta spp.) occur on a great 

 variety of plants, such as Clovers, Vetches, Flax, Hop, 

 Gorse, Ling, Bedstraw, Thyme, Thistles, and Nettles ; and 

 they may be so abundant as to do great damage to crops. 



Total parasites, like total saprophytes, show how de- 

 generate and modified the vegetative organs become in 

 plants which have thus changed their mode of nutrition. 

 The flowers show little or no modification except in colour, 

 and much of the energy they derive from the ' host ' is 

 expended in the production of an abundance of seeds. 

 Partial parasites and partial saprophytes are more common, 

 and show intermediate stages of modification according 

 to the degree of parasitism or saprophytism they have 

 reached. 



Insectivorous plants. In a variety of ways plants may 

 entrap small animals. In the Toothwort, as we have seen, 

 there are cavities in the back-rolled leaves into which 

 small animals may enter. In the Teasel, the bases of the 

 opposite leaves are united in such a way as to form a cup 

 which contains water, and insects, finding their way into 

 the cup, may become drowned. Often flower-stalks are 

 covered by glandular, sticky hairs to which small insects 

 adhere and die in large numbers. Some species of Silene 

 have received in consequence the popular name of ' Catch - 

 fly '. In other plants more specialized traps are found, 

 and the insects or other small animals caught in them may 

 contribute by their decay to the nutrition of the plant. 

 Species which possess such peculiarly modified leaves or 

 shoots and supplement their nitrogenous food in this way 

 are known as insectivorous or carnivorous plants. 



