62 



THE AMERICAN BOTANIST 



Suspending Mendel's Law. — Mendel's Law, redis- 

 covered no longer ago than 1900 has already become about as 

 familiar to the general public as the Darwinian Theory, largely 

 because of the vogue it has had among dabblers in eugenics. 

 The law is so simple that it is surprising that its existence was 

 not earlier discovered on purely theoretical grounds. When 

 two species possessing characters that differ in any respect, such 

 as colored and colorless flowers, are crossed, one character be- 

 comes dominant over the other and the resultant progeny there- 

 fore resemble the dominant parent. When, however, the mem- 

 bers of this new generation are bred together, the missing or 

 recessive character is likely to appear in one-fourth of this 

 second generation. This is explained by assuming that all the 

 plants resulting from the original cross had the potentialities of 

 both parents, though only one of each differing pair of charac- 

 ters could appear at first, but when these latter plants are bred 

 together, the uniting cells pair in such a way that some plants 

 receive only characters derived from one parent, other plants 

 received only characters derived from the other parent, while 

 still others have, like the first generation, mixed characters, one 

 of which is dominant over the other. If cells containing only 

 elements likely to produce white flowers united with other cells 

 of the same kind, only plants with white flowers could result. 

 The same would be true if the uniting cells or gametes carried 

 only the elements for red flowers ; only red flowers could result. 

 Now, the scientists have found a way of suspending the work- 

 ings of this law by fertilizing the second generation from one 

 of the original parents. The next generation, then, cannot pro- 

 duce both dominant and recessive plants, for the new union 

 does not give an opportunity for the characters of the two 

 original parents to separate out in pairs. The uniting gametes 

 from the fertilizing parent are all of one kind. By this method 

 when a desirable cross is obtained, no risk need be run that the 

 next generation will produce two varieties of the plant. This 



