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THE POPULAR SCIENCE MONTHLY 



bear the recessive character. One half of the egg cells, likewise, con- 

 tain the dominant, and one half the recessive character. 



Now, if we could pick out at random an}'- one hundred pollen or 

 male cells to fertilize any one hundred egg or female cells, Ave can see 

 that there are equal chances for four results. A dominant male cell 

 might meet a dominant female cell, a dominant male cell a recessive 

 female cell, a recessive male cell a dominant female cell, and a recessive 

 male cell a recessive female cell. 



We have (D + D), (D + E), (E + D), and (E + E) plants 

 formed in equal quantities, but as the two middle terms are the same, 

 we can reduce the formula to one (D + D) to two (D + E) to one 

 (E + E). But wherever there is a D present in the germ cell, the 



Fig. 3. The Course of the Pollen-tube in a Rock-rose {HeUanthcmum mari- 

 folium). After Kerner and Oliver. 1, single flower; 2, essential organs of flower: 

 course of pollen tubes shown diagrammatically ; 3, pollen tubes penetrating the tissue 

 of the pistil ; 4, dried pollen grain ; 5, pollen grain germinating ; 6, ovule. 



dominant character shows, while the recessive character is hidden. The 

 one part or 25 per cent, of the individuals showing the character 

 (D + D) will appear just like the two parts or 50 per cent, of the 

 individuals having the character (D + E). Therefore, there will be 

 75 per cent, of the individuals which will show the dominant or D 

 character, while 25 per cent, will show the recessive or E character. 

 These 25 per cent, showing the E character will ever after breed true, 

 because they contain nothing but the recessive character; while of the 

 75 per cent, showing the dominant character, one third or those having 

 the pure (D + D) character will breed true in succeeding generations, 

 while the other two thirds having the (D + E) or hybrid character 

 will again split in the next generation. 



For all practical purposes in plant breeding the mere fact of segre- 

 gation is of greatest importance and the complexity of recent Mendelian 



