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S. IKENO : 
Unexpected individuals are mostly dominant forms derived from recessive 
ones. These phenomena are, as I tliink, to he explained chiefly by the 
so-called “reverse mutations” or simply “reversions,” by which I mean the 
return of a form to its original form from which it has been derived by 
mutation. 1 As the magenta variety of Portulaca will in all probability be the 
original wild form, from which other colour-varieties have been derived by 
mutation (so-called “ loss-mutation ”) by one or several steps, such process, as 
the production of magentas or reds from whites is to be called a “ reverse 
mutation.” As I am just beginning to study such phenomena in Poiivlaca 
the explanations given below which are yet largely hypothetical and provisional 
are merely trials for indicating some possible ways of such changes. Many 
breeding experiments 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 Table VIII. 
Each of them is prefixed with an * ; those without an * are presented here 
for the first time. 
1 Reversions in the meaning here employed have been studied in Antirrhinum majus 
(de Tries, die Mutationstheorie, Bd. 1, p. 494), Mirabilis Jalapa (Correns, Ber. d. Deutsch. Bot. 
Ges., Bd. 28 ; 1910, pp. 418-434), Zea Mays (Emerson, Amer. Naturalist, Toi. 51,1914, pp. 87-115 ; 
Genetics, Toi. 2, 1917, pp. 1-35), Oryza sativa (Terao, Amer. Naturalist, Tol. 51, 1917, pp. 690- 
698), and Blantago major variegata and contracta (Ikeno, Genetics, Tol. 2, 1917, p. 413 ; Berne 
générale de Botanique, Tome 32, 1929, pp. 49-56). 
