Spindle and Cytoplasm 95 



Another view is obtained from the 1-hour and 5-hour treatments 

 A\ith Spitwcia root tij)s. In these cases metaphases were plotted dur- 

 ing recovery. Complete recovery occurred within 48 hours it" exposure 

 was 1 hoin-, but (k5 to 66 hours were required for a 5-hour exposure.^ 



Cytological c()nse(]uences in relation to treatment have been ana- 

 lyzed. The first teiraploid cell begins a second cvcle after 30 hours.^-^ 



^•v.•.■^v;^;.;;Srv 



Fig. 3.8 — Recovery stages in ceils of roots of Triticum treated with colchicine. A. Multi- 

 polar groups of chromosomes, unequal numbers. B. Cell with a larger number of 

 chromosomes showing that several cycles of c-mitosis had been accomplished. Upon re- 

 covery, cell plates may form between groups. C. A large cell cut into several smaller 

 ones, a characteristic recovery pattern. D. One cell divided into at least six cells upon 

 recovery from the efFects of colchicine. These cells do not survive but are replaced by 

 diploid, tetraploid, or octoploid cells. (Drawings adapted from photomicrographs of Beans 

 and King, 1938. Their Figures, 31, 32, 34, 35) 



octoploids at 72 hours/'^ and after 96 hours, 16-ploid cells, or 128 

 chromosomes, were in division. ''^^ 



If one studies the entire root, some new facts come to our atten- 

 tion that are more meaningful than any absolute ratio between time 

 and number. Eu|)loid numbers, multiples of 8, predominate so that 

 usually the count reads 16, 32, 64, 128, etc. There are very few poly- 

 ploid cells near the root tip; in fact, after 72 horns diploid cells per- 

 sist a little farther from the tij). Tetraploid and octoploid cells j)er- 

 sist in e\en larger numbers. At the region farthest fiom the tip. where 

 lateral root initials are found, giant lobed nuclei were plentiful.''^ 

 1 hese cells were crowded with chromosomes having as high as lOOO 

 c-pairs. ■"'■"' '•' In these cases no regeneration of the cell took place. As 

 a rule, the nearer the root tip. the lower the chromosome number. Or 

 in other words, a greater percentage of cells with high numbers is 

 found in older portions fjf the root. 



