No. 518] 



VARIATION 



75 



Table V. 



Progeny of a Selfed Ear of Leaming Maize having 20 Rows 



Classes of rows 12 14 16 18 20 22 24 26 28 30 



No. of ears 1 5 4 53 35 19 5 2 1 



pendent in their inheritance. There is no reason why it 

 should not be considered to be of the same nature as 

 various other size characters in which variation seems to 

 be continuous, but in which relatively constant gradations 

 may be isolated, each fluctuating around a particular 

 mode. But this particular case possesses an advantage 

 not held by most phenomena of its class, in that there is a 

 definite discontinuous series of numbers by which each 

 individual may be classified. 



Previous to analyzing the data from pedigree cultures, 

 however, it is necessary to take into consideration several 

 facts. In the first place, what limits are to be placed on 

 fluctuations? 7 From the variability of the progeny of 

 single ears of dent varieties that have been inbred for 

 several generations, it might be concluded that the devia- 

 tions are very large. But this is not necessarily the case ; 

 these deviations may be due largely to gametic structure 

 in spite of the inbreeding, since no conscious selection of 

 homozygotes has been made. There is no such variation 

 in eight-rowed varieties, which may be considered as the 

 last subtraction form in which maize appears and there- 

 fore an extreme homozygous recessive. In a count of the 

 population of an isolated maize field where Longfellow, an 

 eight-rowed flint, had been grown for many years, 4 four- 

 rowed, 993 eight-rowed, 2 ten-rowed and 1 twelve-rowed 

 ears were found. Only seven aberrant ears out of a 

 thousand had been produced, and some of these may have 

 been due to vicinism. 



On the other hand a large number of counts of the 

 number of rows of both ears on stalks that bore two ears 

 has shown that it is very rare that there is a change 



