EVOLUTION OF ANGIOSPER.MS THROU(ai APOSPORY 1 73 



of the adults. That there is no essential distinction between 

 the vegetative and the floral internodes, has long been recog- 

 nized. The flower leaves may take on at times the green color 

 and firmer texture of the vegetative organs, as often happens 

 in roses and trilliums, or the carpels themselves may function 

 as green expanded leaves after opening to scatter their seeds, 

 as in Sterculia, or they may take on functions of the cotyledons 

 or of the endosperm by storing nourishment for the use of the 

 young plant of the next generation, as in the long-persistent 

 pericarps of Sechium and Melocanna. 



The individual angiosperm, like the individual worm or cen- 

 tiped, is a doubly composite organism. It is not merely a colony 

 or complex of cells, but also a combination of a number of 

 theoretically equal and equivalent body-parts or metamers, such 

 as the internodes of the plants and the segments of the animals. 

 The cells are associated into metamers, and the metamers are 

 combined into the complete organism, just as the individual ants 

 or bees join to make the still higher social unit or colony. 



In the internodal metamerism of the angiosperms only one 

 metamer is formed in the ^^^ or embryo and the others are added 

 by subsequent vegetative propagation. In the segmental meta- 

 merism of arthropods the association is more complete, in that 

 numerous metamers are formed in the egg and usually few are 

 added afterward, or none at all. Thus among the millipeds and 

 centipeds where metamerism is very highly developed the larvae 

 of some groups are hatched with only three leg-bearing seg- 

 ments and the others supplied by intercalation at subsequent 

 periods of moulting. But in other families, including those 

 which have the largest number of joints, the young leave the 

 egg with the full complement of segments. In the suborder 

 Geophiloidea the number of segments ranges between 31 and 

 173, far exceeding the number of internodal joints of many 

 plants. 



In many of these lower types of animals a relative equality of 

 the body metamers has been preserved, but in the higher groups 

 the metamers become specialized and unequal. Similar ine- 

 qualities exist in plants, even among vegetative metamers. Thus 

 in numerous plants such as coffee, cacao, cotton and the Cen- 



