CHAPTER IX 

 THE FLOWER AND INSECT-POLLINATION 



91. Evolution of the flower. Perhaps the most con- 

 spicuous feature of Angiosperms is the endless variety of 

 flowers. In fact, the 130,000 different kinds of Angiosperms 

 are largely distinguished by their flowers, which means that 

 there are many thousands of different kinds of flowers. In 

 an elementary book, therefore, it is possible to consider 

 only flowers in general. We recognize the fact that flowers, 

 starting with the strobilus condition, have changed in many 

 directions, and it is not difficult to recognize some of the 

 conspicuous directions. With these in mind, any flower 

 examined will show to the observer the amount of progress 

 it has made, and the general direction it has taken. 



92. Primitive flowers. If changes in flowers are to be 

 noted, some starting point must be established. It is natural 

 to suppose that the most primitive flowers are those nearest 

 the strobilus condition. This means that the sporophylls 

 (stamens and carpels) are numerous, arising from a more or 

 less elongated axis ; that they are entirely separate from one 

 another ; and that beneath them there arises the perianth 

 that distinguishes a flower from a strobilus. This perianth 

 consists of members that are entirely separate from one an- 

 other, and these members are all alike, forming more or less 

 of a rosette beneath or around the sporophylls. Probably 

 in the most primitive flowers the perianth consisted of bract- 

 like members, neither delicate in texture nor brightly colored. 



It is from some such condition that the changes in flowers 

 started, and the most conspicuous changes are indicated in 

 the five following sections. 



151 



