G. ROY LANE 



An analysis was made of the frequency of mitosis (after the usual colchicine 

 treatment) and of micronuclei in the resting cells at different time intervals 

 after doses of diepoxide {Table II and Figure 4). This shows that mitosis is 

 suppressed by the diepoxide, the duration of the effect being dependent 

 upon the dose. It can be seen that the frequency of mitosis is reduced from 

 that of untreated samples. Mitosis drops to a minimum at about 24 hours 

 after 20 minutes' treatment and recovers by about 36 hours. It rises still 

 higher right up to 60 hours. After 30 minutes' treatment the recovery is 

 slower, whereas after 10 minutes' treatment the mitotic frequency has already 

 climbed to a high level and the cells in mitosis appear to be already of the 



30 mn. treatment 

 20 m\r\ treatment 



12 



78 



2t- 



30 se f-2 



Time internal 



fS 



S¥ 



SO 

 h. 



Figure 4. Frequency of mitoses and of micronuclei after treatment with 

 M 1 2, 000 di{2 : 3-epoxypropyl) ether for 20 minutes and 30 minutes 



T2 cell generation. This indicates that after this dose, suppression is of still 

 shorter duration. 



The different degree of mitotic suppression with different doses means 

 that it is dangerous as with X-ray effects to draw comparisons between the 

 effects of different doses at one given time period after treatment. 



The data obtained on the frequency of micronuclei after treatment also 

 show the effect of dose in retarding mitosis. At 30 hours the frequency is 

 less than after the larger dose. 



SURVEY / 



The data so far obtained on the effects of diepoxide on the meristematic 

 root cells of Tradescantia raise many questions to which there is as yet no 

 certain answer. It is useful, however, to consider these questions in order 

 to clarify the direction which future investigation should take. 



271 



