SUPPLEMENT 



a man was persecuted as a heretic if he did not consider our world 

 as the center of the universe, and man, the creature for -whose benefit 

 all the rest of the universe was created. So flowers existed for the 

 gratification of man's sense of beauty, or possibly their color might 

 indicate some magical qualities, but no one 1 bought of the use of 

 flowers to plants, nor of the use to flowers of their beauty, fragrance, 

 and infinite variety of form and color. Obviously, flowers exist for 

 the production of seed, but the significance of the opening of flowers, 

 the fact that they expose their essential organs to the atmosphere 

 instead of uniting sperm and egg cells within closed receptacles, 

 could not be understood until, in our own times, the principles of 

 nature's preference for cross fertilization had become recognized. 

 Given the key, a study of the various means for carrying out this end, 

 involving as it does the marvelous relations between flowers and 

 insects, has become a fascinating pursuit to naturalists. 



As remarked before, actual observation of the process of fertiliza- 

 tion, that is of the union of the egg and sperm cells, requires skillful 

 microscopic work, for both kinds of cells are imbedded in tissues, 

 since they must be protected from the atmosphere. If sufficiently 

 thin sections of pistils during the process of fertilization can be cut, 

 it is seen that the pollen grain germinates on the stigma, sending out 

 a tube which makes its way through the tissues of style and ovary, and 

 through the micropyle of the ovule, so that one of the two protoplasts, 

 or rather spermatoplasts, at the end of the tube may be brought into 

 contact with the egg cell in the ovary ; the nuclei of these two cells 

 fuse, and it is now possible for the growth of the embryo to begin. 



The conveyance of pollen from anther to stigma, on the other 

 hand, can be easily observed, especially in our climate of almost 

 constant sunny weather, and interest is almost sure to grow with 

 observation. Very few flowers indeed are restricted to self-pollina- 

 tion ; inconspicuous, greenish flowers may depend on the wind for 

 cross pollination though insects often help in the pollination of 

 flowers that usually escape the notice of human kind. Flowers con- 

 spicuous for color or fragrance, and those that provide honey, are, in 

 our climate, almost always sure to receive insect help. This fact, 

 together with many devices and adaptations, will appear as we study 

 the individual flowers in this and in succeeding chapters. 



Perhaps some preface is necessary with regard to the uses of color 

 to flowers. That other colors than green serve to render flowers con- 

 spicuous, and so point them out to flying insects, cannot be doubted, 

 but it must not be concluded that color in flowers can have no other 

 use or significance. Red and kindred colors convert light into heat 



50 



