STUDIES OF SEED-PLANTS 199 



In the four-o'clock seed the hard outer wall has developed 

 from the wall of the ovary, the inner coat is the real seed-coat. 

 In the buckwheat the " hull," which is commonly removed 

 before the seed is marketed, is formed from the wall of the 

 ovary. In the bean flower, which is an example of an ovary 

 with many ovules, a number of egg-cells are usually fertilized 

 and begin development at about the same time. While the 

 ovules are developing into seeds, the wall of the bean ovary 

 elongates and becomes the pod. 



In all flowering plants the fully-developed ovary with any 

 part of the flower which develops with it is called a fruit( 212). 



190. Special Adaptations of Flowers. Study of such 

 simple flowers as those of the lily family and of the 

 bean plant have shown the essential organs and work of 

 flowers as reproductive structures. In order to adapt 

 flowers of plants under special conditions to the all-important 

 work of reproduction, there have been developed numerous 

 modifications ; and to some of the most interesting of these 

 special adaptations we shall now give some attention. Most 

 important of the adaptations are those which in some way are 

 related to securing proper pollination. 



191. Flowers and Insects. Many of the most wonderful 

 adaptations of flowers are in relation to insects. There is a 

 mutual advantage in this relation. The insect secures food 

 (pollen and nectar). Some insects like moths and butter- 

 flies, which have a long " tongue," visit flowers for the nectar ; 

 others like the bees and wasps collect both nectar and pollen. 

 On the plant side, the advantage arises from the fact that 

 while getting food the insects brush pollen from anthers upon 

 stigmas, thus producing pollination and very frequently 

 cross-pollination (placing pollen of one flower on stigma of 

 another flower of the same species). 



192. Advantage of Cross-pollination. Many experiments 

 have proved that plants from seeds which originated through 

 cross-pollination are usually better than those resulting from 



