i88 PLANT HYBRIDIZATION BEFORE MENDEL 



curs, the more seeds are produced, and the hybrids springing from 

 them are the more fertile up to a certain limit, self-fertilization 

 producing, as a rule, plants with less fertility and vegetative vigor 

 than cross-fertilization with a nearly related variety. Crossing 

 within the same variety is, for the most part, less favorable than 

 crossing with a nearly related variety. 



5. "If at the same time different kinds of pollen get upon the stigma, 

 only that one becomes operative which has the greater sexual affinity." 

 {lb., p. 210.) 



When two kinds of pollen reach the stigma, the one alone is 

 effective that has the greater sexual affinity. Consequently, the 

 presence of pollen of the same species excludes as a rule the 

 possibility of hybrid fertilization through another species. Since 

 fertilization through pollen of weaker affinity takes place more 

 slowly, therefore pollen of stronger affinity which arrives some- 

 what later may function likewise, and seeds of two kinds be pro- 

 duced in one plant. 



6. "The peculiar operation of the male material affects exclusively 

 the germinal vesicle fertilized by it, and makes itself manifest therefore 

 only in the embryo, and in the plant grown out of it." {ib., p. 213.) 



The operation of the male fertilizing material affects only the 

 embryo-sac, and makes itself evident only in the embryo and the 

 plant growing therefrom. The later changes are the same, no 

 matter what the source of the pollen may be. (ib.) 



7. "The hybrid sprung from the commingling of two different parental 

 forms stands between the two in its systematic characters. For the most 

 part, it holds about the middle position ; more seldom, it has received 

 from one of them a preponderating share, so that it resembles the one 

 parental form more than the other." {ib., p. 214.) 



A cross arising from two different parental forms stands be- 

 tween them in respect to the systematic characters, generally more 

 or less in the middle ; more seldom one or the other parent has a 

 preponderant share, so that it resembles it more than the other 

 parental form ; this being more strikingly evident in variety- than 

 in species-hybrids. In hybrid breeding, either every character oc- 

 cupies an intermediate position, or a part of the characters ap- 

 proach the one, a part the other parental form. In the latter case, 

 the division often occurs in such manner that the vegetative or- 

 gans (stems and leaves), more nearly correspond to the one, or 

 the reproductive (flowers and fruits), to the other. In general, the 



