FERTILIZATION. 163 



honey. Those flowers which secrete nectar do so by means 

 of nectar-glands, small organs whose structure is something 

 like that of the stigma, situated usually near the base of the 

 flower, as shown in Fig. 145. Sometimes the nectar clings in 

 droplets to the surface of the nectar-glands ; sometimes it is 

 stored in little cavities or pouches called nectaries. The 

 pouches at the bases of columbine petals are among the most 

 familiar of nectaries. 



201. 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 four-o'-clock 



° _ , Fig. 145. — Stamens and Pistil 



and the evening primrose, are sweet- of the Grape (magnifled), with 



scented to attract night-flying moths. * toney-gland between each 

 ^ -^ *^ pair of stamens. 



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 brownish colored) to attract flies. 



202. Colors of Floicers. — Flowers which are of any other 

 color than green 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 infrequently, as in 

 some cornels and Euphorbias, the involucre is more brilliant 

 and conspicuous than any part of the flower strictly so-called. 



