uy TYPES OF BRITISH PLANTS 
of form and colour with which plants lay themselves 
out to attract insects. The variations in shape of the 
petals are, as you know, endless. They may fuse into 
a tube as in the honeysuckle, mock the shape of a butter- 
fly as in the sweet-pea, sit round in a symmetrical row 
as the buttercup and the wild rose, or take on such quaint 
shapes as those of the Snap-dragon and the Calceolaria. 
Just as much variety is displayed in their colour; every 
hue, and almost every combination of hues, may be seen 
in our English flowers, whether growing wild or in our 
gardens, and almost always we have to thank the petals 
for it. One colour is never found in England, nor do I 
know of a case given in foreign floras. We have no 
flower that is altogether black. We have deep violet, 
deep purple, and rich brown, but we have nothing like 
black. Yet, as we know, there are plenty of coal-black 
insects, black birds, and black animals. For some reason 
or other, the plant world seems disinclined to follow their 
example. Perhaps part of the explanation may be that 
such a flower would not succeed in fulfilling what we 
shall find later to be one of the chief duties of corollas, 
namely, to attract insects. 
These are the three outer envelopes: the bracts, which 
are often quite a long way off the flower itself, but 
always on the flower-branch; the calyx with its sepals, 
the usually green cup which holds the flower; the corolla 
with its petals, the usually brightly-coloured crown that 
surrounds the essential organs concerned with seed 
production. 
To these we must now turn, and we may consider first 
such a flower as the Buttercup, where the two kinds of 
machine, the stamen and the pistil, or carpel, are both 
present. 
