122 S. IKEXO : 



Uuexpacted iucli\'idiial3 are mostly dominant forms derived bom recessive 

 ones. These phenomena are, as I tliiuk, to be explained cliiefl_A- l\v the 

 so-called " reverse mutations " or simply " reversions," by which I mean the 

 return of a form to its original form fiom which it has been derived by 

 mntatiou.^ As the magenta variety of Porhdaca wiU in all probability be the 

 original wüd form, fi-om which other coloiu'-varieties have been derived l.iy 

 mntatiou (so-called " l(3S3-mntation ") In- one or several steps, such process, as 

 the production of magentas or reds fi-om whites is to be called a " revei-se 

 mutation." As I am just beginning to study such phenomena in Podvlaca 

 the explanations given below which are A-et largely hypothetical and provisional 

 are merely trials for indicating some possible ways of such changes. Many 

 breeding exj^eriments would of course be necessary in order to settle the 

 question definitely. 



Though in the course of my description all such cases met with were 

 generally denoted with an *, they are collected below in the Ta1)le '\TII. 

 Each of them is prefixed with an * ; those without an * are presented here 

 for the first time. 



1 Etversions in the meaning here employed have been sturlied in Antirrltinum majus 

 (de Vries, il'v: ^^utationslheo>•h•, Bil. 1, yi. 494), ^[b■nhi'.h JnUqxi (Coeeens, Jier. d. Deiitxch. Bot. 

 Ges., 13a. 28; 1910, pp. 418-434), Zca iVoi/.s- (Emerson, .liner. :\"(to-n(;s<,Tol. 51, 1914, pp. 87-115; 

 Genetics, Vol. 2, 1917, pp. 1-35), Oryza saliva (Tekao, Amci: yaturaU.st, Vol. 51, 1917, jip. 690- 

 698), nnd Planlago majcn- variegata nnd contracta (Ikeno, GtiwHcf, Vol. 2. 1917, p. 413 ; Heme 

 gin^ale 'le BotaniqtK, Tome 52. 1920, pp. 49 5G). 



