292 PLANT HYBRIDIZATION BEFORE MENDEL 



The "characters" which Mendel, after careful consideration, 

 finally selected for his work were the following: 



1. The form of the ripe seeds (i.e., of the ripe cotyledons), whether 



(a) round, or (b) wrinkled. 



2. The color of the ripe seeds (i.e., of the ripe cotyledons within the 

 transparent seed coats), whether (a) yellow, or (b) green. 



3. The color of the seed coat, whether (a) gray or brown, with violet- 

 red flowers, or (b) white with white flowers. 



4. The form of the ripe pods, whether (a) inflated, or (b) constricted, 

 between the seeds. 



5. The color of the unripe pods, whether (a) green or (b) yellow. 



6. The difference in the position of the flowers, whether (a) distributed 

 along the main axis, or (b) bunched at the top of the stem in a false 

 umbel. 



7. The difference in length of stem, whether (a) 6-7 ft. in length, or 



(b) ^^.y^ ft. 



Each two "differentiating characters" as they are called, in the 

 seven pairs, were tested by crossing. It may be interesting to no- 

 tice how many crosses were actually made. 



1st character-pair — 60 crosses on 15 plants 



2nd " — 58 crosses on 10 plants 



3rd " — ^35 crosses on 10 plants 



4th " — 40 crosses on 10 plants 



5th " — 23 crosses on 6 plants 



6th " — 34 crosses on 10 plants 



7th " — 37 crosses on 10 plants 



In all the seven classes of cases, reciprocal crosses were made. 



Mendel calls attention to the fact that previous experiments 

 with hybrids showed that, as a rule, hybrids were not exactly in- 

 termediate between their two parents, and that, with respect to 

 some of the cases, 



". . . One of the two parental characters is so preponderant that it is 

 difficult, or quite impossible, to detect the other in the hybrid." (p, 342.) 

 "This," he adds, "is precisely the case with the pea hybrids. In the 

 case of each of the seven crosses, the hybrid character resembles that of 

 one of the parental forms so closely that the other either escapes obser- 

 vation completely or cannot be detected with certainty." (p. 342.) 



The character which became evident in the hybrid, Mendel 

 called the dominant., and the character that remained latent, the 

 recessive. He calls attention to the fact that the dominant char- 

 acter is unaffected by the direction of the cross — that it makes no 

 difference whether the parent bearing the character that becomes 

 dominant in the hybrid is used as the pollen parent or as the 



