242 PRACTICAL COURSE IN BOTANY 
EXPERIMENT 82. Dors ODOR INFLUENCE INSECTS? — Try the same 
experiment with different odors, removing the bright colors and sprink- 
ling some kind of perfume on each pane. Try also the effect of decay- 
ing meat and other malodorous substances. Are any insects attracted by 
these? What kinds? Does this account for the noisome smells of the 
“ garrion-flower’’ and skunk cabbage? What kinds of insects are attracted 
by sweet-smelling substances? Do the greater number appear to be at- 
tracted by these, or by foul odors? Are flowers of the sweet-smelling 
or the foul-smelling kind more common in nature? Do insects seem to 
be more strongly influenced by colors or by odors? 
276. The color of flowers, being an adaptation to changing 
external conditions, is a very unstable quality, and varies 
greatly within the limits of the same species. Even on the 
same stem, flowers of different colors are often found, due, 
probably, to hybridization. Yet, notwithstanding all this 
apparently random intermingling of hues, the range of color 
for each species is confined, approximately, within certain 
limits. Nobody has ever seen a blue rose or a yellow aster; 
and though the florist’s art is constantly narrowing the ap- 
plication of this law, it still remains true that in a state of 
nature, certain colors seem to be associated together in the 
floral art gamut. Yellow is considered the simplest and 
most primitive color in flowers, and blue the latest and 
most highly evolved. Yellow, white, and purple, in the 
order named, are the commonest flower colors in nature; 
blue, the rarest. Do you see any relation between these facts 
and the color preferences of insects? 
277. Advantages of insect pollination. — It is evident that 
this is a much more certain as well as a more economical 
method of securing pollination than through the haphazard 
agency of wind or water. In probing around for the nectar 
or the-pollen upon which they feed, these busy little creatures 
get themselves dusted with the fertilizing powder, which they 
unconsciously convey from the stamen of one flower to the 
pistil of another. Insects usually confine themselves, as far 
as possible, to the same species during their day’s work, and 
since less pollen is wasted in this way than would be done by 
