Insects and Flowers 
567 
provided for it, as in the case of violets, where horn-like outgrowths from 
the two lower stamens secrete the nectar and pour it into a cup formed by 
the base of the lower petal. 
“The nectaries may occur on any part of the flower, but they are most 
frequently found at the bases of the stamens, petals, and ovaries, and rarely 
on the calyx. In the plum and peach they form a thick inner lining of 
the cup-shaped receptacle. In nasturtiums the nectar is secreted in a long 
spur from the calyx. 
“Some flowers of simple construction expose their nectar freely to all 
sorts of insects, but others conceal it in various ways so that it is accessible 
only to insects of certain kinds. A frequent device is to have some parts 
of the corolla close over the way to the nectar so that small insects which 
would not assist in cross-pollination are excluded, and only those which 
are strong enough to push aside the barrier or have proboscides of proper 
construction to thrust past it can obtain the nectar and accomplish the trans¬ 
ference of the pollen.” 
With nectar and pollen ready for the insect the plant has yet to advertise 
its sweets, and for that brilliant colors and attractive odors are relied on. 
An attractive odor for insects is not always pleasing to us: certain Araceae, 
some Trilliums, and others have a carrion-like odor, combined with “dull 
colors often marked with livid blotches or veins like dead animal bodies, and 
these flowers attract flesh-flies and carrion-beetles which are the pollinating 
agents.” It appears from various experiments that odor is the chief factor 
in attracting insects from a considerable distance, and that with the nearer 
approach of the insect color becomes an important guide. Despite the 
poor sight (formation of incomplete images, and this possible only within 
certain limited focal distances) of insects they appear to distinguish colors 
at distances where the forms of objects must be very indistinct to them. 
Once attracted to the flower by odor or color, or by both, the pattern and 
fine color streaks and spots play their part in guiding them to the nectaries. 
(See discussion on p. 580 of the sight and color recognition of insects.) The 
shape of the flower now has also its influence; this it is which compels the 
visitor, in order to get at the nectar, to brush against the pollen, or the stigma, 
or both as the case demands, and thus to render fairly its payment for the 
special food provided. The particular shape and make-up, too, often have 
reference to the necessity of keeping away illegitimate visitors, who would 
drain the secreted stores without recompense. Small creeping insects, as 
ants (very fond of nectar), thrips, and others may be shut out of the nectaries 
by fine, stiff little hairs densely set in the throat of the flower-cup, like those 
on the stamens of spiderwort or at the bases of the stamens of Cohcea scan- 
dens , or may be denied access even to the flower itself by sticky glandular 
hairs on the stem and leaves. I once counted nearly a hundred dead or 
