DEVELOPMENT OF PLANTS 355 



proceed along quite different lines. These various modifications 

 of the simple type of flower have been retained very largely 

 because they are mutually beneficial to the plant and to insect 

 life. In the lower forms, the microspores are scattered by the 

 wind as in the gymnosperms. Such flowers are called anemoph- 

 ilous, meaning wild loving, and are small, very simple in 

 structure and produced in large numbers to ensure the forma- 

 tion of seed. In higher types of flowers, odor and nectar glands 

 appear and bright colors which serve to attract insects. Such 

 flowers are termed entomophilous, meaning insect loving. In 

 this way the spores are carried from one flower to the other 

 by the insect visitors with greater certainty than in the case of 

 the anemophilous plants. The variation in the form of the 

 flower and insect went on hand in hand and so it came about 

 that types of flowers finally appeared that were adapted to special 

 kinds of insects, sometimes to a single species, all other forms 

 being unable to enter the flower owing to its peculiar shape-. 

 This was of the greatest benefit to both plant and insect because 

 the insect will confine its visits to such flowers owing to the 

 food which it alone can secure and the plant is equally fortu- 

 nate, since the microspores will only be carried to flowers of the 

 same kind. So we will expect to find in the following lessons 

 that the highest types of flowers are adapted to special kinds of 

 insects and it would be a natural inference that such plants will 

 be very abundant provided of course that they are also adapted 

 to the present conditions upon earth. 



125. The Gametophyte of the Angiospermae. The angio- 

 sperms have developed along quite distinct lines, but they show 

 such a remarkable uniformity in the development and character 

 of the gametophyte generation that this feature of their life his- 

 tory may be considered at this point as it applies to all forms. 

 The megasporangium, also called the ovule, originates in the 

 cavity of the ovary at various points known as the placenta (Fig. 

 269, A). The structure of the sporangium and the formation 

 of the megaspore is very similar to that of the gymnosperms. 

 More often two integuments are formed and the sporangium or 

 the stalk which supports it becomes curved so that it very fre- 



