188 PLANT LIFE 
from the vine. The filamentous strands in- 
crease at the spot where a flower is to develop, 
and a sort of ball of tissue is formed which 
presently bursts through the rind of the Cissus 
stem. Presently the ball splits open, and 
there grows out from within it a flower bud 
which opens out into the single enormous 
blossom. 
A more familiar flowering parasite is the 
Dodder. This plant infests various hosts, 
e.g. flax, clover, nettles, gorse, etc. It 
rather suggests in appearance bundles of 
pink string thrown at random over the vege- 
tation. It belongs to the convolvulus family, 
and still more or less retains the twining habit 
so characteristic of many of its relatives. But 
whereas the leafy convolvulus merely supports 
itself by twining round its support, the almost 
leafless dodder puts forth suckers where its 
stem is in contact with that of its host, and 
from the central portion of each sucker a 
growth is formed which penetrates the plant. 
In this manner the dodder obtains the whole 
of its food, both water and organic substance. 
Although the dodder is really little more 
than a specialised twining convolvulus, never- 
theless, in relation to its parasitic habit, it has 
ceased to form green leaves, and it is not even 
rooted in the soil. It is true that when the 
seed first germinates it is anchored by hairs 
to the ground, but the lower part of the stem 
soon dies away, and the whole plant comes to 
be absolutely dependent on a parasitic life. 
