332 SIGNIFICANCE OF SEXUAL REPRODUCTION [V. 



which produces the flower arises from the same idioplasm 

 which also forms its germ-cells, we can readily understand 

 why the latter should contain the same hereditary tendencies 

 which were previously expressed in the flower which produced 

 them. The fact that variations may occur in a single shoot 

 depends upon the changes explained above, which occur in the 

 idioplasm during the course of its growth, as a result of the 

 varying proportions in which the ancestral idioplasms may be 

 contained in it. 



Fritz Miiller's observation affords a beautiful confirmation of 

 this view, for if the flower itself transmitted the hexamerous 

 condition to its germ-cells, we could not understand why some 

 of the extremely rare hexamerous flowers were produced by 

 the crossing of two pentamerous flowers, in the control ex- 

 periment. An explanation of this fact can only be found in 

 the assumption that the germ-plasm contained in the mother 

 plant, during its growth and consequent distribution through all 

 the branches of the colony, became arranged into a combina- 

 tion of idioplasms, which, whenever it predominated (as it did 

 at certain places), necessarily led to the formation of hexa- 

 merous flowers. I will not consider here the question as to 

 whether this combination is to be looked upon as an instance 

 of reversion, or whether it represents something new. Such 

 a question is of no importance for our present purpose ; but 

 the hexamerous flowers of the control experiment prove, in 

 my opinion, that germ-plasm containing the requisite com- 

 bination was distributed in the mother plant and also existed, 

 but in insufficient amount, in shoots which did not produce any 

 hexamerous flowers. 



Appendix V. On the Origin of Parthenogenesis ^ 



The transformation of heterogeny into pure parthenogenesis 

 has obviously been produced by other causes as well as by 

 those mentioned in the main part of this paper. Other and 

 quite different circumstances have also had a share in its 

 production. Pure parthenogenesis may be produced without 

 the intermediate condition of heterogeny. Thus, for example, 

 the pure and exclusive parthenogenesis with which the large 



' Appendix to page 297. 



