in Hybridisation 91 



its progeny. By this process the species A would change 

 into the species B. Gartner alone has effected thirty such 

 experiments with plants of genera Aquilegia, Diantkus, 

 Geum, Lavatera, Lychnis, Malva, Nicotiana, and CEnothera. 

 The period of transformation was not alike for all species. 

 While with some a triple fertilisation sufficed, with others 

 this had to be repeated five or six times, and even in the 

 same species fluctuations were observed in various experi- 

 ments. Gartner ascribes this difference to the circumstance 

 that "the specific [typlsche] force by which a species, during 

 reproduction, effects the change and transformation of the 

 maternal type varies considerably in different plants, and 

 that, consequently, the periods within which the one species 

 is changed into the other must also vary, as also the number 

 of generations, so that the transformation in some species 

 is perfected in more, and in others in fewer generations." 

 Further, the same observer remarks "that in these trans- 

 formation experiments a good deal depends upon which type 

 and which individual be chosen for further transformation." 

 If it may be assumed that in these experiments the 

 constitution of the forms resulted in a similar way to that 

 of Pisum, the entire process of transformation would find 

 a fairly simple explanation. The hybrid forms as many 

 kinds of egg cells as there are constant combinations 

 possible of the characters conjoined therein, and one of 

 these is always of the same kind as the fertilising pollen 

 cells. Consequently there always exists the possibility with 

 all such experiments that even from the second fertilisation 

 there may result a constant form identical with that of the 

 pollen parent. Whether this really be obtained depends in 

 each separate case upon the number of the experimental 

 plants, as well as upon the number of differentiating 

 characters which are united by the fertilisation. Let us, 



