Techniques of Colchicine Treatment 383 



absence of repeated chromosome counts in various organs. It ap- 

 pears surprising that the bone marrow, the skin, or the cornea was 

 not chosen for chromosome counts and that so many pubHcations 

 and claims rest on such meager technical data. 



B. Techniques in Plants 



16B.1: Solutions Used 



Compared with warm-blooded animals, cells of plants tolerate 

 relatively strong concentrations of colchicine. The substance diffuses 

 rapidly through plant tissues and may be translocated in the plant 

 through the vascular system. Active concentrations remain in con- 

 tact with the cells for a longer time than is recorded by the total 

 exposure to the drug. Apparently tlie effects of colchicine are re- 

 tained for a long time. Penetrability, its low toxicity, and retention 

 in the cell, along with the complete recovery through reversibility by 

 the cell, are unique qualities of colchicine for doubling the number of 

 chromosomes in plants. 



Successful procedures have favored stronger solutions applied for 

 shorter periods over the dilute ones applied during long exposure.^- ^• 

 9. 11. 13, 1.5, IS, 21, 22, 24, 2.5, 26, 27, .30, 17, 3.3 Schedulcs with specific concen- 

 trations advocated and exposure recommendations are given in the 

 papers. If a universal c(jnccntration were selected for treating plants, 

 the strength would be 0.2 jjer cent acjueous solution. This con- 

 centration, or one close to it, has been used more frequently than 

 any other. Wide ranges are effective, but there is an optimum which 

 produces the highest percentages of changed cells. Generally, one 

 gram of colchicine is dissolved in 500 ml. water. The length of time 

 for keej)ing cells in contact with the drug varies from 24 to 96 hours. 

 In addition to concentration and exposure, the growing conditions 

 of a particular tissue are important. Cells must be in a high state of 

 cell division for maximum effective use of colchicine. i- 



A study of the action of colchicine iqoon mitosis requires the use 

 of wide ranges in concentration in order to obtain mininuun, opti- 

 mum, and maximum effects. The objectives are somewhat different 

 from using the drug as a tool for making polyploids. 



The carrier used for colchicine in treating seed plants may be 

 water, emulsions, agar, or lanolin. Whetting agents have been used 

 effectively. Sometimes the addition of glycerine has been recom- 

 mended. '^ The enudsions are sprayed on to the plants or lanolin 

 pastes applied, as suitable. Aqueous solutions are applied by drop- 



