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GENETICS IN RELATION TO AGRICULTURE 



It consisted of absence of yellow and decrease of red in the younger 

 leaves of a few plants. Six of the 15 patterns that arose as bud mutations 

 also appeared more or less frequently as fluctuating variations on certain 

 plants. The derivations of the various color patterns are shown by the 

 diagram in Fig. 160. It will be noted that the original pattern, No. 2, 

 is described as green-yellow-red blotched which means green center, 

 yellow marginal border and red blotches on the epidermis. In the same 

 way the description of pattern No. 4 is interpreted as green center, yellow- 

 spotted marginal border and red blotches on epidermis. 



The frequency with which these various bud mutations occurred is 

 shown in Table LIV. Here are indicated under "Plants" the number 

 of plants in which each type of change might have occurred, under 

 "Frequency," the actual number of bud mutations that did appear, and, 

 finally, the ratio of bud mutations to constant buds. This ratio is 

 obtained by assuming that on the average each plant produced 200 buds. 



TABLE LIV. FREQUENCY OP BUD MUTATIONS PRODUCING NEW COLOR PATTERNS 

 AND LEAF-SHAPES IN COLEUS. (After Stout.) 



Stout remarks that these data indicate the tendencies of the bud 

 variations and give a clew to the behavior of the characters in question. 

 Thus, decrease of yellow occurred twice as often as increase of yellow, 

 and loss of red 2.2 times as often as increase of red. Although these 

 data indicate a tendency toward loss rather than gain of the two colors, 

 the fact that the number of mutations involving gain is about half as 

 large as the number involving loss has considerable interest. It has been 

 generally considered that mutations involving addition of a character are 

 exceedingly rare. While this may be the case in many pure species, it 

 would appear from the above evidence that among the progeny of species 

 hybrids such mutations may be relatively frequent. 



The manner of appearance of these bud mutations was typical of 

 somatic factor mutations. Stout says, for example, "the loss of yellow, 

 loss of green, and gain and loss of red all occurred in single branches and 

 in sections of branches. Frequently two quite different changes occurred 



