Distinction Between Species and Varieties. 587 



It may, however, also happen that in forms whicli 

 differ from one another in two points only, one (^f these 

 would give a bi-sexual union, whilst the other would lead 

 to a uni-sexual cross. Such is the often cited instance of 

 Lychnis zrspertina X diurna. One of the characters 

 '>vould follow Mendel's law in crosses, whilst the other 

 would tend to produce a constant intermediate f(^rm.^ 

 In this case, according to the former character, one parent 

 would be related to the other as a derivate variety, but ac- 

 cording to the latter as a homonomous elementary species. 



Exactly the same, though to a greater extent, must 

 be true of tri-polyhybrids. The points of difference be- 

 tween their parents can be all uni-sexual or all bi-sexual, 

 or some of them uni-sexual and others bi-sexual. In 

 the first case the parents are to be considered as ele- 

 mentary species, in the second as varieties; in the third, 

 however, the principle affords no decision. 



It is just this case which appears to be the commonest 

 in nature. In experiments in hybridization, we must, if 

 we wish at all to elucidate the laws to which the results 

 conform, confine our attention to certain points of differ- 

 ence and leave all the rest out of consideration as of 

 subordinate importance. Mendel did this in his experi- 

 ments with peas, and the same has to be done in crossing 

 Maize, the races of which do not differ from one another 

 exclusively in varietal characters; so also in Lychnis vcs- 

 pcrtina and diurna and in many other cases. 



It would take us too long to continue tin's discussion 

 further, and to accumulate examples; my meaning will. 

 I believe, be sufficiently clear. It may be expressed in 



^T call to mind the Ociiofhcra Pohliaiia (O. lataXhrcristylis) . one 

 of my crosses, the /a/a-character of which hchavcs as a iMiitatiitnal 

 character in a cross ; whilst the shortness of the stamen behaves as 

 a MendeHan character. 



