. Biology and human life. Biology. THE CYCLE OF LIFE: FLOWERS 51 cone-bearing trees, and the catkin-bearing trees. 41. Homology and anal- ogy in the flower. If you have studied several dif- ferent kinds of flowers, you must have noticed the very great differences among petals of different species or among pistils. Indeed, you will often have some difficulty in making up your mind whether some particular structure is one of the regular parts of a flower or something totally dif- ferent. A part of the fas- cination that many peo- ple find in studying new varieties of wild flowers is that of reco
. Biology and human life. Biology. THE CYCLE OF LIFE: FLOWERS 51 cone-bearing trees, and the catkin-bearing trees. 41. Homology and anal- ogy in the flower. If you have studied several dif- ferent kinds of flowers, you must have noticed the very great differences among petals of different species or among pistils. Indeed, you will often have some difficulty in making up your mind whether some particular structure is one of the regular parts of a flower or something totally dif- ferent. A part of the fas- cination that many peo- ple find in studying new varieties of wild flowers is that of recognizing famihar structures under strange disguises, or like that of solving puzzles. Stamens may be large or small, with long filaments or with none, standing freely or fused with one another or with the co- rolla. Similar modifica- tions are found in the other parts. Some stu- dents of plant life go even farther and point out that stamens and carpels, as well as petals and sepals, are special kinds of leaves (see Fig. 25,. Fig. 24. Hand pollenation in the vanilla flower Instead of importing the needed insect to carry on pollenation, the raisers of vanilla decided to hire women and children to go from flower to flower and pollenate by hand. In the orchids the stamens are fused with the stigma, placing the anthers above the stigma in such a way as to make self-pollenation absolutely impossible. an, anther; p, pollen masses; s, stigma. A, gen- eral view of flower; B, position of hands and needle in artificial pollenation; C, needle lifting pollen masses; D, anther raised to expose pollen masses; E, style raised to show opening in stigma; F, longitudinal section to show relative positions of anther and stigma: G, longitudinal section after pollenation, showing pollen masses in the stigma. All the vanilla beans in the Sey- chelles Islands are grown with hand pollenation. Please note that these images are extracted from scanned page images that may have been digitally enhanced for r
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