230 



THE AMERICAN NATURALIST [YOL. LIIT 



per cent, true Mammoth plants which breed true, there 

 is strong reason to believe that the change responsible 

 for ^Nrammoth hal)it of growth has affected one gamete 

 only. If this gamete unites with a normal gamete, then 

 the simple Mendelian ratio would follow, just as in the 

 case of an artificial cross between gametes produced by 

 a Mammoth plant and those of a normal plant. In the 

 one case a portion or all the gametes bearing the Mam- 

 moth character are produced by a normal plant. In the 

 other case, Mammoth plants themselves produce gametes 

 with potential Mammoth characters. In the experience 

 of Honing, normal plants have even produced progenies 

 containing 100 per cent, mammoth plants. This behavior 

 would indicate that all the gametes produced by a mother 

 plant may sometimes become modified to express the 

 Mammoth habit of growth. Although Honing has ob- 

 served the complete disappearance of a line of Mammoth 

 plants which gave rise to progenies of blossoming plants, 

 this behavior has not been definitely observed in this 

 country except as a response to obscure environmental 

 condition>. It is ]iossil)le that the behavior of Honing's 

 inconstant IVrniniiiotli^ i< nf this nature rather than an 

 intei'imi uaiiictic diaiiuv, pcDnanently affecting the hered- 

 ity of the Maintnotli fcntiirc. Until this question is more 

 definitely setth'd, Honing'^ iiicoiistaiit ^rammoth can not 

 be disposed of. 



Since inconstant, intenncliatc plant- behaving as Men- 

 delian hybrids with respect to ]\raninioth character, and 

 sister plants of pure type are known to arise suddenly in 

 the same progeny, there is reason to believe that the 

 clmnge responsible for Mammoth behavior may affect one 

 or both gametes, as the case may bo. Tliis inconstant be- 

 havior of these mutant hybrids is ].ai ticulai ly significant 

 sinee it appears in every way similar to tlic actual be- 

 havior of a controlled cross between a :\rainnioth and a 

 normal plant. Of course, if it is possible for one or more 

 gametes produced by a normal plant to become so modi- 

 fied as to originate a hybrid-mutant or a pure line mutant, 



