Uphof: An Historic Spot 



345 



to be found, 1 observed sporadic indi- 

 viduals of tbe minus mutant, so dif- 

 ferent from tbe typical lamarkiana in 

 leaf form. Figure 6 shows in nature 

 rosettes of OcntJiera lamarkiana, be- 

 tween wbich a mutation, nanclla, is 

 growing". This j^lant was removed to 

 my garden near Amsterdam, where it 

 flourished and produced seed. Its off- 

 sjM'ing were all dwarfs, which empha- 

 sized de Vries' observation that 

 nancUa is one of the most constant of 

 the mutants. 



Between 1910 and 1921 the beech 

 and spruce trees increased considerably 

 in size, whereas the Oenotheras de- 

 creased in number so greatly that it 

 appears that they will become extinct 

 in a few years. It was practically im- 

 possible to get photographs of the 

 few remaining specimens, therefore the 

 accompanying photographs are those 

 of the plants found in 1908. 



As far as I am aware, no photo- 



graphs have CA-er been published of 

 this historical and remarkable place, 

 the starting point for investigations 

 which have figured so conspicuously 

 in modern discussions of the origin 

 of new forms of living organisms. To 

 students of genetics it may be espe- 

 cially interesting to have these pictures 

 reproduced during the month of Feb- 

 ruary, when Hugo de Vries, the found- 

 er of Experimental Evolution, reaches 

 the seventy-fifth anniversary of his 

 birth. 



No doubt all geneticists agree that 

 Dr. de Vries' theory and researches 

 of evolution have thrown a powerful 

 beam on the phenomena of the origin 

 of species. His brilliant discoveries 

 and his revival of Mendel's researches 

 have stimulated scientific investigation 

 and laid the foundation for much suc- 

 cessful work in plant and animal 

 breeding. 



Hybrids and Mutations of Campanula 



INTERESTING results are reported 

 by Lathouwers for experiments with 

 Campanula medium. Hybrids be- 

 tween rose colored and white flowered 

 varieties gave in the first generation 

 dark violet-colored flowers, and in the 

 second generation five classes of flower 

 color are reported, white, rose, dark 

 violet, violet, and lilac in various pro- 

 portions. These results were difficult 

 to understand, but were finally adjusted 

 to Mendelian theories by assuming four 

 genetic factors. A basic color factor, 

 and a "revealer" must both be present 

 to produce color. A third factor is 

 supposed to determine alkalinity, and 

 to be responsible for violet or dark 

 violet instead of rose or lilac. The 



fourth factor is assumed to be an in- 

 tensifier, changing violet into dark vio- 

 let or rose into lilac. 



When the third factor is absent a 

 form called monantha appeared, con- 

 sidered to be a true mutation. It is 

 characterized by a large solitary flower, 

 with no lateral flowers or branches. 

 Suddenly in a pedigree culture after 

 two generations of self-fertilization the 

 mutation was represented by eighteen 

 individuals, while seventy-five other 

 plants retained the normal form. This 

 same mutant form appeared in later 

 generations, and came nearly true to- 

 seed. Crosses were also made with 

 this and other floral abnormalities.^ 



^ See Lathouwers, M. V. Researches Experimentales sur L'Heredite chez Campa- 

 nula medium L. L'Academie Royale de Belgique. No. 1283. 1922. 



