Fig. 19-13. Cereus spachianus. Cells showing increasing chromosome numbers during 

 development, a and b, 2n ; c, 32n; d, 64n; e, highly polyploid resting nucleus from an 

 older portion of the cortex; /, young polyploid resting nucleus with chromocenters, 

 2 to 3 mm. behind the shoot apex; g, a part of the differentiated cortex showing marked 

 differences in cell size, presumably because of somatic polyploidy. ( From Fenzl and 

 Tschermak-Woess. ) 



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