in Hybridisation 353 



CONCLUDING REMARKS. 



It can hardly fail to be of interest to compare the 

 observations made regarding Pisum with the results arrived 

 at by the two authorities in this branch of knowledge, 

 Kolreuter and Gartner, in their investigations. According 

 to the opinion of both, the hybrids in outward appearance 

 present either a form intermediate between the original 

 species, or they closely resemble either the one or the other 

 type, and sometimes can hardly be discriminated from it. 

 From their seeds usually arise, if the fertilisation was 

 effected by their own pollen, various forms which differ 

 from the normal type. As a rule, the majority of individuals 

 obtained by one fertilisation maintain the hybrid form, 

 while some few others come more like the seed parent, 

 and one or other individual approaches the pollen parent. 

 This, however, is not the case with all hybrids without 

 exception. Sometimes the offspring have more nearly 

 approached, some the one and some the other of the two 

 original stocks, or they all incline more to one or the other 

 side ; while in other cases they remain perfectly Like the 

 hybrid 'and continue constant in their offspring. The hybrids 

 of varieties behave like hybrids of species, but they possess 

 greater variability of form and a more pronounced tendency 

 to revert to the original types. 



With regard to the form of the hybrids and their 

 development, as a rule an agreement with the observations 

 made in Pisum is unmistakable. It is otherwise with the 

 exceptional cases cited. Gartner confesses even that the 

 exact determination whether a form bears a greater resem- 

 blance to one or to the other of the two original species 

 often involved great difficulty, so much depending upon 

 the subjective point of view of the observer. Another cir- 

 cumstance could, however, contribute to render the results 

 fluctuating and uncertain, despite the most careful observa- 

 tion and differentiation. For the experiments plants were 

 mostly used which rank as good species and are differ- 

 entiated by a large number of characters. In addition to 

 the sharply defined characters, where it is a question of 

 greater or less similarity, those characters must also be 

 B. H. 23 



