310 



PLANT HYBRIDIZATION BEFORE MENDEL 



Class III has 6 terms or character-combinations, with an average 

 of 43 plants to each such combination. All the groups in this class 

 are constant as to one character and hybrid as to the other two. 

 For example, Group 2i bears the sign AABbCc. This means that 

 the seeds of each of the 45 plants in this group had the following 

 appearance: they were all round (AA), yellow (Bb), and grey- 

 brown (as to seed-coat) (Cc). But since B is hybrid as to color of 

 the cotyledons, and since C is accompanied by c it is hybrid as to 

 seed-color and seed-coat color also. 



Finally, Class IV has one term with 78 plants, each of which is 

 hybrid with respect to all three of the character-pairs. 



The ratios in which the average of the plants in each class stand 

 to one another, of 10:19:43:78, are so close to 10:20:40:80, 

 or 1:2:4:8, that there is no doubt whatsoever that this is the 

 actual ratio. 



It then appears that the actual condition of things in a hybrid, 

 in which three pairs of characters are in question, is a combina- 

 tion obtained by multiplying together the following expressions : 



and 



AA + 2Aa + aa, 

 BB + 2Bb + bb, 

 CC + 2Cc + cc. 



The result is that we get all the possible combinations of these 

 various terms (or character-combinations), to the number of 27, 

 as follows : 



Mendel did not stop here, however, but carried on further ex- 

 periments in which the remaining characters, i.e., pod-characters, 

 height, etc., were also combined by twos and threes, which he says 

 all gave approximately the same results. From these experiments 

 he concludes that : 



