346 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 any one hundred pollen or 
male cells to fertilize any one hundred egg or female cells, we 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+ R), (R+D), and (R+R) 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+ R) to one 
(R-+ R). But wherever there is a D present in the germ cell, the 

Fic. 8. THE COURSE OF THE POLLEN-TUBE IN A ROCK-ROSE (Helianthemum mari-. 
folium). After Kerner and Oliver. 1, sifigle 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+ R). 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 R character. 
These 25 per cent. showing the R 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+ R) 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 
