— 410 — 



ing to this it will be imderstood why so many types from nature 

 are pure in the essential characters and show no segregation. 

 Probably the homozygotes are far more common in nature than 

 originally supposed. 



The principal cultivation experiments were carried out in 

 the Botanical Garden of the University, Copenhagen. 

 The cytological investigations were carried out in the Laboratory 

 oi Genetics of the Royal Veterinary and Agricultural 

 College, Copenhagen, and some of the cultivation experiments 

 from 1922 here mentioned took place at its experimental field 

 at Lyngby. I tender my best thanks to Professor Raunkiær, 

 Director of the Botanical Garden, and to Professor Winge Phil. 

 Dr., Director of the Laboratory of Genetics, for the kindness 

 with which they have placed these institutions at my disposal. 



I thank the "Botanisk Rejsefond" for the kindly aid 

 given me for my statistical and ecological investigations in nature, 

 especially in Jutland, and I thank Mr. C. A. Jørgensen for his 

 kindness in making the three lists from Læsø. 



Copenhagen, the Botanical Museum of the University. Vs- 1922. 



Literature. 



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 Clausen, J., (1921): Studies on the Collective Species Viola tricolor L. 



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