Theory of Plant Breeding 



suits were as follows : 1 141 A, 2 267Aa, 1 140a. A and a 

 being the dominant and recessive characters employed. 



Perhaps the most interesting of the recent papers on 

 this subject is another by the same author. 13 Of 44 

 pairs of Mendelian characters, he shows that 41 (no 

 less than 93 per cent.) maybe explained on the theory 

 that the dominant character is presence and the recessive 

 is absence of some particular unit character which is in 

 most cases a colouring substance. 



Suppose one represents the first generation of hybrids 

 by two buckets with a number of yellow and green 

 counters (half yellow and half green in each). We 

 may then make up the second generation by taking 

 one counter from each bucket at random. By the 

 ordinary laws of probability, the result of a very large 

 number of trials would be such a percentage as 25YY, 

 25YG, 25GY, and 25GG, which is 25 pure yellow, 

 50 yellow-green, and 25 pure green, giving the three 

 to one proportion (for yellow dominates green). 



So that in any case of this sort where two races are 

 crossed which only differ in that one possesses a colour- 

 ing substance, this enzyme (or whatever it may be) would 

 be transferred in three cases out of four. 



Of course it is rash to suppose that the inheritance 

 can be quite so simple as this. The colour is probably 

 produced as a result of enzymes formed by a series of 

 chemical changes. The originator of the series will be 

 passed on to the germ of those that are to possess it. 



When one uses two pairs of characters, the Mendelian 

 results are a little more complicated. Such proportions 

 occur as 9 : 3 : 3 : 1, or 9 to 7 when one dominant 

 is alone considered. 



One of these complex cases has been very beautifully 

 worked out by Miss E. R. Saunders in the case of certain 

 stocks. 14 The characters used were the glabrous or 



303 



