50 PART I. ORGANOGRAPHY. 



THE ORGANS OF REPRODUCTION. 



Introductory. — Nature of the Flower. 



The organs of reproduction in phsenogamous or flowering 

 plants consist of flower, fruit and seed. They constitute a mech- 

 anism, more or less complex, whose function it is to continue the 

 species. To this end, each part of the mechanism is subserv- 

 ient, and each, therefore, has a meaning which we should 

 endeavor to understand. No part of it is so minute or appar- 

 ently insignificant as not to deserve careful attention and thor- 

 ough study. The organs of reproduction are not only interest- 

 ing in themselves, for flowers, particularly, make strong appeals 

 to everyone's sense of the beautiful, and inevitably awaken in 

 thinking minds a desire to understand their structure, but they 

 also furnish us with the most reliable characters for determining 

 how nearly or how remotely, different plants are related to each 

 other ; in other words, for classifying them according to their 

 natural relationships. 



Perhaps nothing in the vegetable world is more wonderful 

 than the immense variety of flowers. But this multiplicity of 

 forms has not always existed. A careful study of the flora of 

 the past, as revealed in its fossil forms, and a discriminating 

 study of the plants of our own time, necessitates the conclusion 

 that all this variety and complexity have arisen from compara- 

 tively few and simple forms. Progressive adaptation to environ- 

 ment has been the law of vegetable life. Plants have been sub- 

 ject to changing conditions of soil and climate. The earth's 

 crust has been slowly elevated in some localities, and depressed 

 in others ; large areas of land have been alternately raised 

 above the sea level and then submerged ; these things have 

 necessitated profound changes in temperature, in atmospheric 

 humidity, and in other conditions affecting plant growth. More- 

 over, plants maintain a continual struggle with each other for 

 the occupancy of the soil — a struggle whose conditions vary, not 

 only with the changing physical conditions in the same locality, 



