to the introduction of foreign pollen. 

 It occurs, for instance, in some rare 

 cases that certain parts of an otherwise 

 quite normally developed flower 

 wither, resulting in a partial exposure 

 of the fertilising organs. A defective 

 development of the keel has also been 

 observed, owing to which the stigma 

 and anthers remained partially uncov- 

 ered.^ It also sometimes happens that 

 the pollen does not reach full perfec- 

 tion. In this event there occurs a 

 gradual lengthening of the pistil dur- 

 ing the blooming period, until the 

 stigmatic tip protrudes at the point of 

 the keel. This remarkable appearance 

 has also been observed in hybrids of 

 Phaseolus and Lathy rus. 



The risk of false impregnation by 

 foreign pollen is, however, a very 

 slight one with Pisiim, and is quite in- 

 capable of disturbing the general re- 

 sult. Among more than 10,000 plants 

 which were carefully examined there 

 were only a very few cases where an 

 indubitable false impregnation had oc- 

 curred. Since in the greenhouse such a 

 case was never remarked, it may well 

 be supposed that Bruchi/s pisi, and pos- 

 sibly also the described abnormalities 

 in the floral structure, were to blame. 



[Fi] THE FORMS OF THE HYBRIDS ^ 



Experiments which in previous years 

 were made with ornamental plants 

 have already afforded evidence that 

 the hybrids, as a rule, are not exactly 

 intermediate between the parental 

 species. With some of the more strik- 

 ing characters, those, for instance, 

 which relate to the form and size of 

 the leaves, the pubescence of the 

 several parts, &c., the intermediate, in- 



MENDEL 



deed, is nearly always to be seen; in 

 other cases, however, one of the two 

 parental characters is so preponderant 

 that it is difficult, or quite impossible, 

 to detect the other in the hybrid. 



This is precisely the case with the 

 Pea hybrids. In the case of each of the 

 seven crosses the hybrid-character re- 

 sembles ^° that of one of the parental 

 forms so closely that the other either 

 escapes observation completely or can- 

 not be detected with certainty. This 

 circumstance is of great importance in 

 the determination and classification of 

 the forms under which the offspring 

 of the hybrids appear. Henceforth in 

 this paper those characters which are 

 transmitted entire, or almost un- 

 changed in the hybridisation, and 

 therefore in themselves constitute the 

 characters of the hybrid, are termed 

 the dojmijant, and those which become 

 latent in the process recessive. The ex- 

 pression "recessive" has been chosen 

 because the characters thereby desig- 

 nated withdraw or entirely disappear 

 in the hybrids, but nevertheless reap- 

 pear unchanged in their progeny, as 

 will be demonstrated later on. 



It was furthermore shown by the 

 whole of the experiments that it is 

 perfectly immaterial whether the dom- 

 inant character belongs to the seed- 

 bearer or to the pollen-parent; the 

 form of the hybrid remains identical 

 in both cases. This interesting fact was 

 also emphasised by Gartner, with the 

 remark that even the most practised 

 expert is not in a position to determine 

 in a hybrid which of the two parental 

 species was the seed or the pollen 

 plant." 



Of the differentiating characters 



s [This also happens in Sweet Peas.] 

 ^ f Alendel throughout speaks of his cross- 

 bred Peas as "hybrids," a term which many 

 restrict to the offspring of two distinct 

 species. He, as he explains, held this to be 

 only a question of degree.] 



^^ [Note that Mendel, with true penetra- 

 tion, avoids speaking of the hybrid-character 

 as "transmitted" by either parent, thus escap- 

 ing the error pervading the older views of 

 heredity.] 



11 [Gartner, p. 223.] 



