270 TEXTBOOK OF BOTANY 



for instance, are very different from the single wild flowers 

 from which they have been developed. The odors of flowers, 

 too, are a means of letting insects know of their presence. 

 Most of the odors that are attractive to insects are also, 

 fortunately, pleasant to us. The odors of certain flowers 

 are another reason why we have chosen for cultivation the 

 plants that bear them. Some flowers, like carnations, are 

 conspicuous to both sight and smell. Other plants, like 

 mignonette, have small, inconspicuous flowers which attract 

 insects chiefly by their odor. The pleasant-smelling sub- 

 stances contained in many flowers, such as roses, violets, 

 jasmine, and lavender, are extracted and used in the manu- 

 facture of perfumes. Occasionally, however, odors that 

 attract insects are very unpleasant to us ; examples of this 

 sort are the skunk cabbage and the carrion-flower. 



280. Nectar. Although it is true that flowers attract 

 the attention 'of insects by their size, color, and odor, the 

 insects do not visit flowers simply because they are beau- 

 tiful or sweet-smelling. An insect flies or crawls to a par- 

 ticular flower because that flower may be useful to it in some 

 way. Insects find different flowers useful in different ways. 

 Most often the flowers supply them with a special sweet 

 food called nectar. Nectar is produced in various parts 

 of a flower, and in some cases even outside the flower ; but 

 usually it is found in such a place that when an insect visits 

 a flower in search of nectar, some part of its body touches 

 one or more anthers and so brushes off and carries away some 

 of the pollen. The nectar of the horse-chestnut, for ex- 

 ample, is formed at the bottom of the sepals ; that of the 

 cucumber and the pumpkin, in a cup formed by a union of 

 the lower parts of the sepals and petals. The buttercups 

 and lilies produce nectar on the lower part of each petal ; 

 that of the columbine is formed in the lower spur-like end 

 of each petal ; and that of the strawberry in the bottom of 

 the flower, between the stamens and the pistils. Many of 



