| Abstract: | The length of the mitotic cycle and the time spent in mitosisare calculated for six regions of the apical meristem of rootsof Zea. The two methods used are the measurement of the ratesof labelling nuclei with radioactive thymidine and the ratesof accumulation of metaphases in roots grown in colchicine.The mitotic cycle lasts from 12 hours in the cap initials toabout 200 hours in the quiescent centre of the same roots. Somepoints about the organization of apices are discussed in thelight of these estimates. |
