248 EVOLUTION OF PLANTS 
although the flowers themselves are inconspicuous. 
Many such cases occur in the Euphorbia family, one 
of the most familiar being that of Poinsettia, a common 
greenhouse shrub, having the flowers surrounded by 
numerous large, brilliant red bracts. 
We have already seen that in the more specialized 
types of flowers there is usually a reduction in the 
number of parts, accompanied by a tendency to a coa- 
lescence of the members of each series of floral leaves, 
and this often results in the production of a funnel- 
shaped or tubular corolla which has the nectar secreted 
at the bottom of the flower, where it can be reached only 
by insects having a tongue long enough to probe to the 
bottom of the corolla. Much less frequently this tubu- 
lar form of the flower is due to the cohesion of the 
sepals alone, the petals remaining quite distinct, as we 
see in some of the pink family, ¢.g. the carnation and 
catchfly. A study of such tubular flowers shows that 
they are, for the most part, pollinated through the agency 
of butterflies and moths, although some smaller insects 
may visit them for the pollen. 
The characteristic odors of so many flowers are also 
lures for insects, and sometimes, as in the mignonette, 
this is the only means of attracting attention, as the 
flowers are very inconspicuous in color. Many white 
flowers have a peculiarly strong scent, which is usually 
most marked at night; indeed, some flowers are odorous 
only at night. An examination of these pale, night- 
scented flowers soon reveals the fact that they are espe- 
cially adapted to attract night-flying insects, the white 
or pale yellow color, and strong odor, making them more 
readily found in the twilight, or even after it is quite 
