5 66 
Insects and Flowers 
same flower) different in length so that the pollen would be unlikely to fall 
on the stigmas, or ( d ) the having the stamens and pistils so situate with 
regard to each other that it is difficult or very unusual for the pollen to reach 
a stigma. All these devices are familiar to every student of botany, and 
to gardeners, florists, and flower-lovers generally, and examples of them all 
can readily be found among our common garden and field plants. Any 
simple manual of botany will put one in the way of hunting them out for 
one’s self. 
To recur now to the first of the two principal lines of specialization 
referred to as those which have arisen in connection with the advantage 
of cross-pollination, namely, the modification of the floral structures, we 
shall find these modifications to consist of ( a ) the secretion of nectar to 
attract the insects, ( b ) the development of odor, color, pattern, and shape 
to guide them to the flower and when there to the nectar and pollen in such 
a way as to insure their brushing against both, or either, pollen and stigma* 
(c) the modification of shape so as to prevent the stealing of nectar and 
pollen by non-helpful insects, and ( d ) the blossoming at those times in 
the year (seasonal flowering) when the particularly helpful insects are most 
numerous, and the opening of the flowers at such times, in daylight, twilight* 
or at night, as specifically accords with the food-seeking flights of these 
insects. The manifold variety of these modifications will be indicated and 
illustrated by accounts of a few specific cases exemplifying certain more 
or less distinct kinds of modification and reciprocal relation with insects,, 
but a few general statements may first be made. 
The pollen collected for food by the bees and a few other insects is, of 
course, a normal product of the flower, and it is only necessary that there 
be enough of it to supply the insects and yet suffice for the plant’s own uses, 
i.e., in fertilization. As the oldest, the most primitive, means developed 
among plants to effect cross-pollination, a means still used by all the conifers, 
the grasses, and many other plants mostly characterized by the total absence 
of colored floral envelopes (petals and sepals), is the production of vast quan¬ 
tities of light, non-adherent, pollen grains to be distributed by the wind, 
the more specialized entomophilous flowers (those depending on insects, 
to carry their pollen) probably started with enough and more of pollen to 
supply their own needs as well as the demands of their visitors. 
The nectar, however, is a special product, developed in direct connection 
with the insect pollinating specialization. It is a "more or less watery solu¬ 
tion of sugar and of certain salts and aromatic substances secreted by a. 
special tissue known as the nectary and expelled at the surface through the 
epidermis by breaking down of the tissues, or through a special opening; 
of the nature of a stoma. The nectar either remains clinging to the surface 
of the nectary or it gathers in large drops and falls into a nectar receptacle 
