The Experimental Polyploids 275 



techniques yielded polyploid types/'" The reason these methods were 

 replaced is found in the two specific advantages demonstrated by col- 

 chicine: First, colchicine was very effective for making polyploids 

 Avith many different species; and second, the drug was applied easily 

 to young growing plants Avith very little damage being done to them. 



There are several noteworthy features of colchicine that account 

 for its effectiveness as a polyploidizing agent. Brieflv, colchicine is 

 highlv soluble in water; colchicine is not toxic to plant cells even in 

 strong dosages; colchicine is effective in concentrations ranging from 

 1.0 to 0.01 per cent (1:100 to 1:10,000) ; and finally, it is soluble in 

 lipoids. Furthermore, the effect obtained during a treatment is wholly 

 reversible. Thus the drug is almost "made to order" for changing 

 diploids into polyploids. 



After recovery from treatment the new tissue from treated genera- 

 tions (Co = generation) and the progeny of succeeding generations 

 (Ci = first, Co r= second, etc.) do not show damage of a hereditary 

 nature. The usual changes associated with multiplication of chromo- 

 somes, gigantic characters in leaf, flower, fruit, and seed, are trans- 

 mitted to the next generations; there is no evidence that "deteriora- 

 tion" ^" sets in after colchicine reaches the protoplasm. While the 

 treated plants may perhaps have wrinkled leaves, distorted stems, and 

 various anatomical malformations, such temporary changes disappear 

 in Cj, Co, and later cycles. 



Gene changes or chromosome repatterning have not been proAed. 

 s'^- "1 although preliminary tests led to these suggestions. This much 

 is certain: Changes comparable to those produced by X-ray have not 

 been found, and if we choose to use the word mutation, it must be 

 clearly stated that colchicine does not cause gene mutations. Only in 

 the broad sense of mutation, which includes chromosomal doubling, 

 may we use the term in connection with colchicine as a producer of 

 mutations.--^ If the definition is limited to gene changes and chromo- 

 some repatterning (inversions and translocations) , colchicine does not 

 cause mutations" Hence it is incorrect to classify colchicine with 

 mutagens, such as p-acetamidotropolone, a 7-carbon compound which 

 appears to cause chromosomal breakage.'^ 



More knowledge about the meaning and use of chromosome num- 

 bers in relation to species relationship formation is desirable. Every 

 experimenter before commencing a project Asith colchicine should 

 know the drug is not a chemical fertilizer; it is not a phytohormone; 

 it is not a weed killer; it is not a vitamin; it is not a mutagen; and 

 finally, colchicine is not merely one more organic substance on the 

 present long list now at the disposal of many persons interested in 

 plants.2» The drug has specific and limited uses; therefore, reports 

 giving directions to spray a field with colchicine or to soak the soil 

 as one would witli fertilizing agents, are completely erroneous. 



