DEVELOPMENT OF PLANTS 401 



microspores and therefore replaces the bracts and spathe of pre- 

 ceding orders, but owing to its pecuHar coloration and form, it 

 also serves as an attraction to special kinds of insects. In the 

 preceding forms that attracted insects, the inducements were usu- 

 ally in the nature of shelter and food, which was largely the 

 microspores that were offered freely to all. Such flowers are 

 principally visited by a low order of stupid flies and beetles that 

 are rather promiscuous feeders and are quite as likely to go from 

 a flower of one species to that of a different kind, or to some 

 other object and so defeat the principal object of the flower. 

 With the development of the perianth, however, .the flower is 

 equipped with a device that primarily serves to exclude these less 

 desirable visitors and to attract the more inte ligent ones. In 

 Erythronium the perianth is in a horizontal position, so that it 

 ofTers a natural landing place for the insect, and the inducement 

 is a sugary solution secreted by nectar glands concealed at the 

 base of the perianth. It is an easy task for the more intelligent 

 long-tongued insects, like the bees, wasps and butterflies, to reach 

 the nectar in this type of flower. Such insects come to know by 

 experience how to gather the food from a particular form of 

 flower and consequently they will often confine their attention to 

 a single species during their entire flight; consequently the flower 

 by excluding the less intelligent and slothful insects is more cer- 

 tain of being properly crossed. The development of nectar and 

 also of odor glands is among the important variations that 

 appear in the evolution of the flower. It is chiefly by means of 

 the perfumes derived from these organs that the insect is directed 

 to the flowers. The coloration is also of service, when the insect 

 is near to the flower, thus supplementing the perfume glands by 

 directing him to the proper entrance. Some of the larger and 

 more brightly colored members of this and other orders appa- 

 rently depend entirely upon the attraction of their colors, while 

 other forms rely upon perfumes, the flowers being small and in- 

 conspicuous and often hidden. So we have reached a point in 

 the evolution of the flower where it presents a number of varia- 

 tions that are adapted and of benefit to special kinds of insects. 

 Insects have likewise varied and some have become of special use 

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