XI 
THE SPECIAL COLOURS OF PLANTS 
317 
brownish flowers, some of which smell like carrion, are 
attractive to flies, as the Arum and Aristolochia; while the 
dull purplish flowers of the Scrophularia are specially attrac¬ 
tive to wasps. 
5. Some flowers have neither scent nor nectar, and yet 
attract insects by sham nectaries! In the herb-paris (Paris 
quadrifolia) the ovary glistens as if moist, and flies alight on it 
and carry away pollen to another flower ; while in grass of 
parnassus (Parnassia palustris) there are a number of small 
stalked yellow balls near the base of the flower, which look 
like drops of honey but are really dry. In this case there is 
a little nectar lower down, but the special attraction is a 
sham ; and as there are fresh broods of insects every year, it 
takes time for them to learn by experience, and thus enough 
are always deceived to effect cross-fertilisation. 1 This is 
analogous to the case of the young birds, which have to learn 
by experience the insects that are inedible, as explained at 
page 253. 
6. Many flowers change their colour as soon as fertilised; 
and this is beneficial, as it enables bees to avoid wasting time 
in visiting those blossoms which have been already fertilised 
and their nectar exhausted. The common lungwort (Pul- 
monaria officinalis), is at first red, but later turns blue; and 
H. Muller observed bees visiting many red flowers in 
succession, but neglecting the blue. In South Brazil there 
is a species of Lantana, whose flowers are yellow the first day, 
orange the second, and purple the third; and Dr. Fritz 
Muller observed that many butterflies visited the yellow 
flowers only, some both the yellow and the orange flowers, 
but none the purple. 
7. Many flowers have markings which serve as guides to 
insects ; in some cases a bright central eye, as in the borage 
and forget-me-not ; or lines or spots converging to the centre, 
as in geraniums, pinks, and many others. This enables 
insects to go quickly and directly to the opening of the 
flower, and is equally important in aiding them to obtain a 
better supply of food, and to fertilise a larger number of 
flowers. 
8. Flowers have been specially adapted to the kinds of 
1 Miiller’s Fertilisation of Flowers, p. 248. 
