214 TYPES OF BRITISH PLANTS 
part of the Ivy. But a parasitic farmer would adopt 
a different process. He would cheerfully let the stream 
run on, and encourage his neighbour to water his turnips 
well. But when they were just ready, he would slip in, 
and cart away half of them. 
Having thus explained that certain plants are not 
parasites, we will consider those that can plead no defence. 
Of course it is possible to regard them -really as the 
highest development of plant-life, employing the lower 
orders to do their work, but mankind has a well-founded 
prejudice against slave-owning, and one may note two 
facts about these parasites. In the first place, they are 
totally dependent for existence on other plants, and cannot 
under any circumstances fight their way unaided; and in 
the second place, they have generally lost some organs 
through lack of use. In the same way, if there were 
a country where people never stood, walked, or ran what- 
ever happened, but always insisted on being carried, their 
descendants, if the habit were kept up for many genera- 
tions, would in all probability lose, if not their legs, at 
least the capacity to use them. 
There are three degrees of the parasitic habit, in the 
first of which we find that the plant only takes a small 
amount of tribute from its neighbours. It still has roots 
and leaves, but the former, besides sending up their own 
supplies, take tribute from the roots near them. In the 
second class, all roots are abandoned, and the plant simply 
sends down suckers into the substance of the tree or 
plant on which it rests. But leaves are still kept, and do 
their work. In the third class the plants are wholly | 
dependent on other resources than their own. Joots 
have gone, and leaves have gone, or, to put it more 
accurately, the leaves no longer perform their great duty 
