7 10 Colchicine 



proceeds becomes considerably altered. Cross sections as well as longi- 

 tudinal views are very instructive.!^^ 



Floral parts from CartJiamus tinctorhis follow similar patterns of 

 induced changes when treated with colchicine before the flowers 

 mature. Blunt" wrinkled petals and short, single gynoecia with Avoolly 

 hairs replace the pointed, elongate petals, double gynoecium, and 

 stiff, pointed hairs of normal flowers.'^^ 



Enough data have been collected to confirm the fact that colchi- 

 cine alters the way in which cells enlarge.i^' Growth by increase in 

 volume is modified under specific conditions, and this may be related 

 to changes in viscosity of cytoplasm caused by colchicine.-^' ^-- ^^'^' •^"' ^'^• 



126, 88, 98, 10.3 



To explain the mechanism for a c-tumor, certain jxirallels were 

 drawn between viscosity changes in the cytoplasm and dissociation of 

 the cytoplasmic proteins.i"'^ Colchicine caused a decrease in viscosity 

 that was correlated with the formation of the c-tumor in Allium. In 

 this explanation, a dissociation was the primary causal factor. A 

 similar mechanism was described in connection with the c-mitosis.io3 

 The idea of a narcosis was also introduced to account for a c-tumor, 

 but instead of there occurring a narcotized cell division, it is the 

 growth process by cell enlargement that is infiuenced by colchicine.ios 

 In regard to this hypothesis and the preceding one. much additional 

 information is needed for a full explanation of the action of the drug 

 during cell enlargement. 



4.3: Colchicine-Meiosis and Gametophytic Development 



In pollen mother cells or megaspore mother cells that are in con- 

 tact with colchicine at the time of reduction division, the meiotic 

 stages are converted into a "colchicine-meiosis."'-* Only at this time 

 can such a process as c-meiosis take place (Fig. 4.3) . Earlier, that is, 

 during divisions in the archesporium, and in later cycles, when micro- 

 spores or generative cells divide, the processes become true c-mitoses.'^» 

 Since the c-meiosis represents a special case, primarily because meiosis 

 is a particular kind of division, it is discussed in this chapter with 

 other aspects of growth and reproduction. Obviously the spindle 

 inhibition is common to both c-mitosis and c-meiosis; so also are the 

 c-pairing phenomena (Table 4.1) , a secondary action of the suj^pressed 

 spindle, and the "c-bivalents" accompanying c-meiosis. These and 

 related characteristics of c-meiosis occur only during a certain time in 

 the rejjroductive cycle (Figs. 4.3 and 4.4; I"al)lcs 4.1 and 4.2) .'•'• -•'• 



124, 148 



To help visualize how essential a timing sequence is in producing 

 the c-meiosis, a survey of the particular cell, treated stage, and ex- 

 pected results are given in Table 4.2. From this outline one can see 



