128 BOTANICAL GAZETTE [august 



of a margin is dominant over its absence. It is probable, therefore, 

 that the white margin is due to the presence of an inhibitor whose 

 action is localized in the margins of the petals. 



In 191 1, among 73 pedigreed families of Papaver Rhoeas grown 

 at the Station for Experimental Evolution, 45 resulted from crosses 

 between plants of which the presence or absence of a margin had 

 been recorded, and of which a goodly proportion of the offspring 

 were capable of being similarly recorded. The rest either had one 

 white-flowered- parent whose possession (or lack) of a margin 

 could not be determined by inspection, or for some other reason one 

 or both parents or the offspring could not be safely characterized 

 with respect to margins. Of the 45 families having the margins 

 of parents and offspring recorded, 3 represented crosses between 

 plants both of which had margined petals, 17 were from crosses 

 between one margined and one unmargined parent, and 25 re- 

 sulted from matings between plants none of which had margined 

 petals. The three families from matings between margined parents 

 consisted of 236 individuals, including in each family a mixture of 

 plants with margined and with unmargined petals. Records 

 of the margins were often impossible, owing to the interference of 

 other factors not yet fully investigated, so that the numbers 

 of each type of offspring have no special significance in the present 

 connection and they will be reserved for discussion at another 



time. 



Of the 17 families produced by mating plants with margined 

 and with unmargined petals, 12 were composed of a mixture of 

 plants, some with margins and some without, 3 contained only 

 plants with unmargined petals, and in 2 families practically all of 

 the individuals had margins. With margins dominant over their 

 absence, only two kinds of families were to be expected from this 

 type of mating, namely, all margined if the margined parent 

 chanced to be homozygous, and mixtures of plants with margined 

 and unmargined petals if the margined parent was heterozygous. 

 The three families (10272, 10273, 10274) in which no margins 

 appeared, though one of the parents had a margin, are exceptions. 

 One margined individual was the mother of all three of these 

 exceptional families. The records show that this plant differed 



