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Figure 1 . Photomicrographs of V'icia faba chromosomes in Feulgen squashes oj root lip mitoses {all 



colchicine treated), after treatment with X-raj>s. All X 3,000. 

 (a) Chromatid interchange between long and short chromosomes. Note the short achromatic 



regions at points of exchange, 

 {b) E.xamples of anomalous changes which are difficult to distinguish from chromatid breaks. 



Probable chromatid break at top-left. 

 (c) and {d) The four types of proposed intrachange, with explanatory diagram. 



