CROSSINGS IN MELANIUM-VIOLETS 267 



albomaculata type is nialc or Icinah' parent. In /•':; and later genera- 

 tions this chaiacler did not show any sej^regation: :dl (h'scendiints 

 were all)oina(iilata. Thns, the genetieal l)ehavi(na- ol tliese types is 

 rather ditferent; eommon to all of them is that their mode of inheri- 

 tance does not follow the Mendelian laws. 



The other type, on the contrary, may have the disposition to the 

 alhomaculata-character localized to the nucleus and probahly to the 

 chromosomes. They show Mendelian segregation, when crossed with 

 normal green forms, with dominance to normal gretMi in /•,. To this 

 grouj) belongs the alhomaculata in V///.s ( Rasmlson 1916), Tropivolum. 

 Ipomea and other species (Correns 1919 and 1920), Barbaren 

 (Dahlgren 1921) and the alhomaculata in Viola, here recorded. 



I have grown the alhomaculata form in Viola from seeds obtained 

 from a herbarium, collected in Gotland 1912. In 191.5 I had 3 plants 

 in culture, all alhomaculata. One of these plants was selfed and used 

 for crossings. The selfed descendants were all maculated and have 

 bred true during the five years they have been in culture. The des- 

 cendants, however, are white-maculated in a very different degree. In 

 some plants the white spots were to be seen already on the cotyledons 

 as small white streaks. Others lacked the white spots when young; 

 these spots were only seen when the j)lants begun to flower. 



When a white-spotted leaf was anatomically investigated the 

 origin of the white spots was found to start with the dying away of 

 solitary or groups of pallisade cells. The adjacent pallisade cells 

 turn over and press the dead ones more or less together. The de- 

 struction process proceeds and often it results in the pushing away 

 of the dead tissue together with the epidermis. By this means the 

 leaf often gets an asymmetrical appearance. Very often so large a part 

 of the leaf dies away that only the middle veins remain. So far as I 

 have ol)served only the leaves are white-spotted. I never noticed 

 any white spots on the main axis or on the leaf-stalks. When the 

 leaves on the top of the branches and near the growing point are 

 strongly white-spotted they will often die and fall away. 



The alhomaculata-character gav(> the impression of being a sort 

 of disease not only because of the falling away of the white-sjxjtted 

 parts of the leaves but also on account of the increasing of the white 

 spots with the increasing age of the plants. 



In order to investigate the genetics of the albomaculata-form I 

 crossed it with a normal green V. arvensis. 



The Fi-generation showed dominance for normal green. The 



Heredität IV. 18 



