DEVELOPMENT OF PLANTS 3S3 



towards the center of the plant, a feature doubtless of consider- 

 able advantage to plants living in semi-arid regions. The flower 

 is of a decidedly higher type than any previously studied and it 

 presents several features of special interest. The flower is later- 

 ally placed or slightly pendulous. The perianth is conspicuouslv 

 developed, consisting of two whorls of three members each, 

 though these organs are not as yet fully differentiated into calyx 

 and corolla. The stamens are also arranged in two whorls of 

 three members each and the three carpels form a single whorl 

 which cohere into a compound pistil. The members of these 

 whorls alternate with each other, so that the flower has three 

 planes of symmetry. At maturity the walls of the ovary become 

 papery and split down the side, thus freeing the seeds. This form 

 of fruit is known as the capsule, and is of very common occur- 

 rence in the order (Fig. 287, C). The development of a con- 

 spicuous perianth is a noteworthy departure. It protects the 

 microspores and therefore replaces the bracts and spathe of pre- 

 ceding orders, but owing to its peculiar 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 intelligent ones. In 

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

 offers 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 



