218 THE FAIRY-LAND OF SCIENCE. 
while the evening primrose (CEnothera biennis) and 
the night campion (Silene noctiflora) spread out their 
flowers just as the daisy is going to bed. 
What do you think is the reason of this ? If you 
go near a bed of evening primroses just when the sun 
is setting, you will soon be able to guess, for they will 
then give out such a sweet scent that you will not 
doubt for a moment that they are calling the evening 
moths to come and visit thei.i. The daisy opens by 
day, because it is visited by day insects, but those 
particular moths which can carry the pollen-dust o* 
the evening primrose, fly only by night, and if this 
flower opened by day other insects might steal its 
honey, while they would not be the right size or shape 
to touch its pollen-bags and carry the dust. 
It is the same if you pass by a honeysuckle in the 
evening ; you will be surprised how much stronger its 
scent is than in the day-time. This is because the 
sphinx hawk-moth is the favourite visitor of that 
flower, and comes at nightfall, guided by the strong 
scent, to suck out the honey with its long proboscis, 
and carry the pollen-dust. 
Again, some flowers close whenever rain is coming. 
The pimpernel (Anagallis arvensis) is one of these, 
hence its name of the "Shepherd's Weather-glass." 
This little flower closes, no doubt, to prevent its 
pollen-dust being washed away, for it has no honey ; 
while other flowers do it to protect the drop of honey 
at the bottom of their corolla. Look at the daisies 
For example when a storm is coming on ; as the sky 
grows dark and heavy, you will see them shrink up 
and close till the sun shines again. They do this 
