78 PLANTS AND ANIMALS 
food-supply wholly from animals are indeed rare, save 
near the bottom of the vegetable scale, and most of 
such parasites are minute; one of the most noticeable 
in our own country is the fungus Cordyceps militaris, 
which may be found growing on the dead bodies of 
larve or pupe which it has killed—a little scarlet, club- 
shaped plant, about an inch in height. But some of 
the most highly organized plants obtain portions of 
their food-supply from animal sources. Mention has 
already been made of the Sundews (Drosera), Butter- 
worts (Pinguicula), and Bladderworts (Utricularia), 
which capture live insects, etc., by means of sensitive 
organs (as in the first two cases) or ingenious traps 
(as in the last), and subsequently digest them, and 
they will be dealt with later on (p. 186). Then there is 
the Venus’ Fly-trap (Dion@a) and the well-known 
Pitcher Plants (Nepenthes), which actively, as in the 
former case, or passively, as in the latter, catch insects 
and digest them, by means of leaves modified in very 
extraordinary ways. In all these instances the advan- 
tage lies entirely on the side of the plant, just as in 
the case of most of the plant-eating animals the advan- 
tage is wholly with the animal. But in a large number 
of instances—many of them of a most interesting 
nature—the inter-relations are such as to benefit both 
the actors, each obtaining from the other what is 
useful to it. One of the most conspicuous and wide- 
spread relationships of this kind is that prevailing 
between flowers and insects, the insect receiving food 
in the form of nectar, and at the same time carrying 
pollen from flower to flower, without which transfer 
no fertile seed would be formed. To this interchange 
of favours we shall return later (p. 81); meanwhile, it 
