1022 



2. The observer may liave wrongly estimated the difference in 

 the number of factors of the P-forms, so that tlie nnmerical pro- 

 portion he expects, is wrong. 



3. Characters have to be dealt with, which cannot be seen at 

 the same moment in different individuals. If the observations in 

 such a case are extended over too sliort a period of time, then 

 wrong results are obtained. 



4. In consequence of a strongly thictuating variability of characters 

 the observer has failed to distinguish the different genotypes with 

 sufficient sharpness. 



The known cases in which the cause of the deviation lies in the 

 plant itself, are the following. 



J. There are fewer gametes of a particular kind formed than 

 ought to arise. The deviation then already arises in the formation 

 of the sexual-products. 



2. The union of some kinds of gametes comes about with more 

 difficulty than that of others. The deviation then lies in the fertili- 

 sation-process. 



3. Certain combinations of gametes are less capable of life than 

 others, so that the young indixiduals die off before the character 

 can be observed. 



4. The different genes may be coupled or may repel one another. 

 Of all the various phenomena here enumerated examples are 



known. B.\t:h ^) and os|)ecially Pi.atf, ^) give a survey of them in 

 their lextbooks. 



The case, which 1 wish lo deal willi here, belongs to the second 

 group, in which the cause of the deviation lies in the plant itself. 

 The nature of this cause will be made clear below. 



The phenomenon appeared on the crossing of a white- and a blue- 

 flowering variety- of Litmm usitatis.siinum and related to the colour 

 of the flower. The blue-flowering form was a variety obtained from 

 Egypt, and has been described by me'') ])reviously and named 

 Egyptian flax. The seed of the variety with white flowers was 

 obtained from Messrs. Vilmorin-Andkikux of Paris. Pure lines 

 of both varieties were used for the investigation and the i-eciprocal 

 crossings were carried out in 1908 and in 1911. The whole nuud)er 



Ï) E. Baur, Vererbungslebre. 1911, p. 116. 



2) L. Plate, Vererbungslehre. 1913, p. 194. 



■') Der Flachsstengel, eine statistisch anatomische Monographie. Verh. v. d. HoU 

 Maatsch. d. Wetensch. Haarlem, Verz. 3, Deel VI, Stuk 4, 19Ü7, p. 2!2. 



Das Verhalten fluktuierend variierender Merkmale bei der Uastardierung Ree. d. 

 Trav. bol. Néerl. Vol. 8, 1911, p. 206. 



