FLOWER AND FRUIT a S38 
with the attracting of insects, without which many 
flowers are unable to produce fruit and seeds. 
The members of the corolla, which vary in number 
according to the flower, may be free or united. In the 
one case they are apopetalous and in the other 
synpetalous, the former, well seen in the buttercup, 
being a more primitive condition than the latter, 
which is strikingly exhibited in the foxglove. It is 
from the corolla, as a rule, that the flower takes its 
characteristic form, and from it usually arises its 
perfume. Where the petals are symmetrical, both as 
to size and arrangement, as in the buttercup and apple, 
the flower is said to be actinomorphic (Gk. aktinos a 
ray and morphe form), and where this is not the case, 
as in the pea and snapdragon, it is zygomorphic 
(Gk. zygon a yoke). The zygomorphic form is less 
primitive than the actinomorphie, and is obviously 
more adapted to arrest the attention of insects. 
Attraction.—Insects visit flowers for their food— 
either nectar alone, as in the ease of moths and butter- 
flies, or nectar and pollen, as is the case with bees; 
but, in every instance, it is the size, shape, colour, or 
perfume of the flower that indicates where the food 
is to be found. To show the part played by the petals, 
remove the corollas from some of the flowers on a 
plant commonly visited by insects. The flowers so 
mutilated will be passed over, though their near 
neighbours may be visited repeatedly. The experi- 
ment is not so conelusive as it appears, for, by removal 
of the petals, there is generally taken away the support 
on which the insect stands while gathering its food. 
Different insects show a partiality for different colours, 
and one has only to watch a mixed flower border for 
an hour or so to see that the bees prefer blue and 
violet, are indifferent to yellow, and seem to avoid 
searlet. Searlet sweet peas intermingled with blue 
are left unvisited, while the latter swarm with bees. 
