DEVELOPMENT OF PLANTS 459 



because of their protective armor of prickles, bitter, acrid juices 

 or oils and resins. Especially to be noted is the seed-like fruit 

 with its numerous devices for distribution. All these features, 

 among - others, explains their extensive distribution in open coun- 

 tries. Without doubt the greatest advantage appears in the struc- 

 ture of the flower and the inflorescence. The highest type of a 

 flower, as in the case of a machine, is the one that is most efficient. 

 The flower is not so elaborate as the orchid or as those of some 

 other groups, but it is superior because it accomplishes its work 

 with greater certainty and more economically. Reduction has 

 been made in every part without loss of conspicuousness and 

 variations have also appeared that practically eliminate the uncer- 

 tainties of crossing and autogamy, and consequently the forma- 

 tion and distribution of the seed is ensured. In a word, every 

 evolutionary tendency that you have noticed in the development 

 of the flower finds its expression in this group of plants. 



