individuals. Further consideration convinces 

 me that this restriction is highly undesirable 

 because it is impracticable. It would be quite 

 impossible to know for a certainty that two 

 twigs used as cuttings or cions from the same 

 tree had the same genotypic constitution, and 

 consequently there could be no security in the 

 assumption that they were members of the 

 same clone, if the definition given in my pre- 

 vious note should be maintained. I wish, 

 therefore, to offer an amendment to that defi- 

 nition by striking out such restriction. The 

 definition may then read : " Clone, a group of 

 individuals traceable through asexual repro- 

 ductions (including parthenogenesis when un- 

 accompanied by genotypic segregation) to a 

 single ancestral zygote, or else perpetually 

 asexual." This definition puts the word 

 " clone " on exactly the same footing as the 

 expression "pure line," making it a purely 

 genealogical term and involving no implica- 

 tion whatever as to the genotypic equality of 

 the individuals included in the single clone. 



GEO. H. SHULL 



