Presumptive Mutations in Wild & Cultivated Plants 67 



var. perlittcscens, which is yellow throughout, that the yellow palate 

 was dominant. Thus yellow palate is dominant in one species and 

 recessive in the other a quite unexpected result. It is evident 

 that dominance or recessiveness cannot safely be used in deter- 

 mining which is the original or parental type. Even though these 

 are parallel mutations, the alternation in dominance probably 

 depends on an effect of the other specific differences. 



In Digitalis purpurea several varieties, evidently mutations, 

 have been studied. Saunders (1911), Shull (1912) and others 

 have bred the form called by Chamisso heptandra in 1826. The 

 flowers are characterized by dialysis and staminody of the corolla, 

 giving a flower with a petaloid upper lip and seven stamens. But 

 many flowers of a heptandrous plant may show the abnormality 

 in varying degrees, like a wave of reversion advancing up the plant. 

 This variety is a recessive in inheritance. 1 A form nudicaulis with 

 smooth stems and leaves less hairy on the upper surface is found by 

 Miss Saunders (1918) to be a simple dominant to the type. Although 

 this condition corresponds to the half-hoary type in stocks, yet in 

 the latter it is due to several factors and behaves as a Mendelian 

 recessive to hoary. This is another example of externally similar 

 characters which are wholly different in their genetic relationships, 

 and it shows that certainty regarding variety relationships can 

 only be attained by actual breeding experiments. D. purpurea 

 nudicaulis occurs wild in various parts of England mingled with 

 pubescens, the hairy type. The latter is usually more abundant and 

 the indications are that nudicaulis has originated from it as a 

 mutation. That a new dominant character can arise by a mutation 

 is known from the case of (Enothera rubricalyx among plants or 

 such mutations as bar eye in Drosophila among animals. 



From an almost unlimited number of cases of new varieties or 

 forms probably originating as mutations in wild species and often 

 already in process of spreading, we may select a few almost at 

 random. 



1 An exactly parallel mutation has long been known in a North American 

 member of the Ericaceae, Kalmia latifolia. In 1871 Asa Gray (Am. Nat. 4 : 373) 

 described a plant from South Deerfield, Mass, showing dialysis with staminody. 

 It was grown in the Arnold Arboretum and figured by C. S. Sargent (Garden 

 and Forest 2 : 452). It seeds freely, but apparently its inheritance has not 

 been tested. In 1909 Stone (Rhodora 11 ; 199) independently reported the 

 same form (var. polypetala Nicholson) from the roadside in Leverett near Mt. 

 Toby, and Rehder (Rhodora 12 : 1, 1910) adds a number of varieties, evidently 

 mutational, of this species. Fernald (Rhodora 15: 151, 1913) records near 

 St. John's, Nfld., a considerable colony of K. angustifolia with white corollas 

 (forma Candida). This form was also found at Sherborn, Mass., and evidently 

 occurs as a sporadic negative mutation which will spread if left to itself. 



