Sentence:  Irregular metamorphoses of flowers are extremely common, and usually consist either of an actual muliplication of petals, or of the transformation of stamens and pistils into petals ; the effect of these chages being the formation of double flowers, the <WSD>impletion</WSD> of which appears to take place in different ways in different plants. 
Meaning of the word marked with <WSD> tags:  An act of filling; the state of being full.