276 Colchicine 



In this chapter and the next iour chapters the future possibilities,^^ 

 limitations, and accomplishments are given. Miracles were predicted 

 in the numerous writings in praise of colchicine, but there often 

 followed a serious disillusionment for those not informed in poly- 

 ploidy and cytogenetics.^^ A wave of great enthusiasm for colchicine 

 in some quarters was succeeded by a loss of interest. Totally dis- 

 counting colchicine, however, is quite wrong. 



n.2: Terminology 



In the rapidly expanding field of cytogenetics, new terms are con- 

 stantly being added, while others are modified as more information 

 is acquired. The two terms, auto-syndesis and allo-syndesis, have been 

 used with exactly opposite meanings by two groups. Now each time 

 the terms are used, an explanation must accompany the usage. When 

 autopolyploidy and allopolyploidy were first pointed out by Kihara 

 and Ono in 1926,^=^ the distinctions were based on materials at hand. 

 When many more examples came into consideration, the differences 

 were not as specific as one might desire for a classification. Terms and 

 their meanings often introduce added confusion. The terminology 

 and definitions used here have in large part been adapted from Clau- 

 sen, Keck, and Heisey.^^ Extensive work on terminology has been 

 done by Stebbins.*"^ 



Ploidy, in recent usage, means /o/r/ (from the Greek pJoos) and 

 a combining form like (oid) . Thus the prefixed word polyploidy 

 means many-jold. This refers to the number of sets of chromosomes 

 for a particular plant or animal. Monoploid refers to those cells or 

 individuals with one set; diploid, twofold; triploid, threefold; tetra- 

 ploid, fourfold. Then autoploid means self-fold; ainphiploid, both- 

 fold. 



Polyploidy describes a serial relation of numbers in multiples 

 starting from some basic number. If the number is 7, then the poly- 

 ploid series would read 21, 28, 42, for triploid, tetraploid, and hexa- 

 ploid, respectively. 



Autoploidy is an abbreviated form of the term autopolyploidy and 

 will be used for those polyploids formed by nudti plication of sets of 

 chromosomes within the limits of a species. Admittedly, the range is 

 wide, and complications arise in classification because the autoploid 

 with four homologous sets will differ from the one derived from two 

 subspecies, that is, the doubled intraspecific hybrid. 



Amphiploidy embraces the polyploids derived from the additions 

 of two distinct species. A sterile hybrid AB upon doubling becomes 

 the amphijiloid AABB. If the number of species included increases 

 beyond two, a polyploid-amphiploid condition obtains. 



