BARBERRIES. 



789 



Fig. 17. At this stage we should also expect the flowers to be 

 solitary, arising each from the axil of a leaf very similar to the 

 rest of the plant's foliage. 



Competition in securing the benefits of insect visits, together 

 with the possibilities of a more economical as well as more 

 effective disposition of tissue-building material, would conspire to 

 bring about through natural selection the following changes : 



1. Those branches of the herb on which flowers appeared 

 would be given up more and more fully to their function of 

 flower production ; their subtending leaves would be reduced in 

 size, and through a shortening of the axis the flowers would be 

 brought closer together, and thus their conspicuousness enhanced. 

 At the same time, part of the material saved might go to form 

 additional flowers in the cluster. With the assumption of the 

 shrubby habit the floral branches (peduncle, rhachis, and pedi- 

 cels) retaining their herbaceous nature, in consequence of their 

 short-lived usefulness, would appear still less like the others. 

 The formation of flower buds to last over the winter would favor 

 the blossoming of the flowers more nearly together in the follow- 



FIG. 17. 



FIG. 18. 



FIG. 17. Diagram showing number and arrangement of parts in the primitive berberidaceous 

 flower. Bracts, three (heavy black) ; sepals, six (outlined) ; stamens, twelve, dehiscence 

 longitudinal ; carpels, six, many-ovuled. 



FIG. 18. Diagram of flower (hypothetical) in a stage of evolution intermediate between the 

 primitive form and the highest barberry type. Bracts and sepals as before; stamens, 

 twelve, with valvular dehiscence and bearing nectar glands (heavy black) ; carpel, one, 

 many-ovuled. 



ing year. As the subtending leaves would now have lost almost 

 the last vestige of their usefulness, we should expect their reduc- 

 tion to mere scales. The result of all this would be such a ra- 

 ceme as we find the barberry to possess (Fig. 2). 



2. With the increase in the number of flowers in a cluster 

 there would be less need for so many pistils in each flower. It 

 might often happen that only a few of those in one flower would 

 be fertilized, and in that case the store of food could be increased 

 in the favored seeds, much to the advantage of the offspring pro- 

 duced. Pistils which ceased to have a use would gradually dis- 



