ECOLOGY OF FLOWERS oat 
called nectaries. ‘The pouches at the bases of columbine 
petals are among the most familiar of nectaries. 
428. Odors of Flowers. — The acuteness of the sense of 
smell among insects is a familiar fact. Flies buzz about 
the wire netting which covers a piece of fresh meat or a 
dish of syrup, and bees, wasps, and hornets will fairly 
besiege the window screens of a kitchen where preserving 
is going on. Many plants find it possible to attract as 
many insect visitors as they need without giving off any 
scent, but small flowers, like the mignonette, and night- 
blooming ones, like the white tobacco and the evening 
primrose, are sweet-scented to attract night-flying moths. 
It is interesting to observe that the majority of the flowers 
which bloom at night are white, and that they are much 
more generally sweet-scented than flowers which bloom 
during the day. <A few flowers are 
carrion-scented (and purplish or brown- 
ish colored) and attract flies. 
429. Colors of Flowers. — Flowers 
which are of any other color than green 
probably in most cases display their 
colors to attract insects, or occasionally 
birds. The principal color of the flower Ie: 
is most frequently due to showy petals; Fie. 250.— Stamens and 
2 F : Pistil of the Grape 
sometimes, as in the marsh marigold, it (magnified), with a 
belongs to the sepals; and not infre- fect" Wuanayg be 
quently, as in some cornels and Eu- **™en* 
phorbias (Fig. 245), the involucre is more brilliant and 
conspicuous than any part of the flower strictly so called. 
Different kinds of insects appear to be especially 
attracted by different colors. In general, dull yellow, 
