Stout: The Origin of Dwarf Plants 443 



ond generation dwarfs not like Oe. nanella is also the rule in crosses 

 between Oe. nanella and Oe. Hookeri, Oe. CockereUi, Oe. cruciata 

 and also Oe. biennis w^hen the latter is the seed parent. 



When Oe. nanella is fertilized by pollen from Oe. biennis the Fi 

 is composed largely of dwarf plants. In the earlier crosses De 

 Vries reports a few tall plants and many dwarfs (1913. P- 241) but 

 from a cross in 1907 he obtained only dwarfs which, however, he 

 classed in two types, Oe. semialta and Oe. debilis, each of which 

 was different from the Oe. nanella parent. In this case the con- 

 dition of the alia pangen in the hybrids is assumed to be inactive X 

 labile, which is the same condition assumed for Oe. nanella X Oe. 

 Lamarckiana. 



De Vries finds in such behavior evidence of the production of 

 new species in groups by hybridization. He assumes that a few 

 pangens are involved and that those exist in few conditions. The 

 integrity of such units can only be assumed by calling in such all- 

 sufilicient properties as lability and inactivity which admit of very 

 sporadic behavior. 



It is generally assumed that a new elementary species arises 

 suddenly without transitional forms. This is not the case with the 

 dwarf type of Hibiscus here described. The plant No. i from 

 which all dwarf plants thus far obtained have arisen, possessed a 

 few of the characteristics of the dwarf. The next generation gave 

 dwarf, intermediates and robust plants in quite irregular numbers 

 in the two series grown. Bartlett (191 5) describes two dwarf 

 types arising in a progeny of Oe. Reynoldsii, one of which (semialta) 

 is intermediate in general stature and has leaves less reduced than 

 in the extreme dw^arf form (debilis). Variations such as these are 

 not like ordinary fluctuations in giving a frequency distribution 

 agreeing with Quetelet's law and they do not conform to the 

 Mendelian ratios of segregation, although as Bartlett points out, 

 there is much in the behavior that suggests the segregation assumed 

 by Mendelian interpretation. They are irregular and sporadic 

 variations involving different degrees and intensity of change. The 

 most marked of these involve changes affecting the character of 

 several organs. 



Further evidence regarding irregular expression of characters is 



