1024 



is always less llian was to be expected, or as we may also consider 

 it, the number of blue-flowering ones is grealer. Since here however 

 the former case obtains, as will be shown later, I shall indicate the 

 deviation in future as a deficiency of white-flowering plants. Further 

 it is seen from the tabic that the deviations, with the exception of 

 one small culture, are considerable. For the whole number of 

 observations on 800 white and 3106 blue ones the deviation calculated 

 for these figures amounts to +0.181. The mean error for this 

 number is 0.027 ; the deviation is therefore about 6.3 times greater. 

 This shows that the deviation from the ratio cannot be ascribed to 

 chance, but that a definite cause must exist. The question is now 

 what this cause is. Of the four causes mentioned aboxe, which 

 result from errors or wrong suppositions, three do not here come 

 into consideration. With regard to the first, the number of observations 

 is very great, with regard to the second the flowering of all of the 

 plants was observed and with regard to the third cause fluctuating 

 variability plays no role here. The only remaining cause therefore 

 is a wrong hypothesis as to the number of factors in which the 

 i^- forms differ. For it is possible that the numerical ratio to be 

 expected is not 1 : 3, and that therefore we have not to deal 

 with a monohybrid crossing or with a poly hybrid behaving as a 

 monohybrid, but that here several factors occur, which cause the 

 blue colour of the flower. The number of gametes in which the 

 factors for blue are wholly absent will then be relatively smaller 

 and white-flowering plants will arise in the second generation in 

 smaller proportion than in monohybrid crossing. In the case in 

 which the number of factors for blue amounts to two, each by itself 

 producing the colour, the proportion of white and blue in F^ is 

 1 : 15, whilst with three factors for blue the proportion is already 

 1 : 63. These proportions differ so much from the obser\'ed ones, 

 that the cause must be different. Also when it is assumed that the 

 blue colour is caused by still more factors, which separately or in 

 definite groups can produce this colour, ratios are obtained which 

 do not in the least agree with that which was observed. If indeed 

 the existence is assumed of a very great number of factors which 

 oidy produce blue when combined in a certain way, a ratio may 

 be arrived at which sufflcientl}' agrees with the given one. Such 

 an assumption would only liave a reasonable basis, when the 

 phenomenon could not at all be explained in an other way. I have 

 found, however, that we are not dealing here with complicated 

 relations of factors, but that there are two other causes, which 

 together produce the deficiency of white-floweriiig plants. 



