MORPHOLOGY OP LEAVES AND FLOWERS 625 



seed, while the awns which represent the calyx become barbed and 

 aid in distribution. In the buttercups the ovary invests the seed 

 while the style forms a hook. The involucre in the clotbur and 

 ragweed remains around the pistils and becomes more or less spiny. 

 In the nightshade {Solanum nigrum) the ovary becomes fleshy and 

 the fruit is called a berry. 



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