ECOLOGY OF FLOWERS 



357 



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 

 is most frequently due to showy petals; 

 sometimes, as in the marsh marigold, it 

 belongs to the sepals; and not infre- 

 quently, as in some cornels and Eu- 

 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, 



FIG. 250. Stamens and 

 Pistil of the Grape 

 (magnified), with a 

 Nectar Gland, g, be- 

 tween Each Pair of 

 Stamens. 



