Kempton : P)ranched Ears in Maize 



251 



of progenies are to l)e exi)ected — those 

 having some plants branched and those 

 without branched plants. Of the thirty- 

 five progenies, eight produced some 

 branched-eared plants and twenty-seven 

 only normals. 



From the ratio of branched to nor- 

 mal-eared plants in the branched-eared 

 strain shown in Figure 5 it seems clear 

 that only about one-fifth of the ])lants 

 in lines carrying the factors for l)ranch- 

 ing exhibit the trait. If this be true 

 for the Pawnee ])o])ulati()n as a whole, 

 then the expected ratio of branched to 

 non-branched progenies in a j^opulation 

 from the self -pollinated non-branched 

 plants with branched eared sibs would 

 be 2.8 to 1, while the observed is 1 to 

 3.4. This latter ratio closely approxi- 

 mates that expected on the basis that 

 branched ears result from the combina- 

 tion of four recessive factors and that 

 the progenies tested were heterozygous 

 for all of them, a condition which fails 

 of support on other counts. With the 

 small number involved it seems idle to 

 speculate further on a possible factorial 

 analysis especially since linked factors 

 or even chromosome redui)Hcation may 

 be involved. 



A single line from one of the eighty- 

 f[ve unbranched ears occurring later in 

 the ]:)edigree has been followed for 

 two generations without branches but 

 such cases require no especial explana- 

 tion. 



It is clear from the pedigree of the 

 branched ear shown in Figure 5 that 

 a line has been isolated from the 

 Pawnee strain which can be relied 

 upon to produce some plants with 

 branched ears irrespective of the na- 

 ture of the immediate parent. There 

 can be little doubt that this type of 

 branching is an inherited character for 



which the original branched ear was 

 homozygous. Repeated self-pollination 

 does not serve to stabilize the amount 

 of branching and the percentage of 

 non-branched plants does not decline. 

 The variability in branching, therefore, 

 cannot be attributed to the influence of 

 hereditary modifying factors and must 

 be considered as a phenomenon of ex- 

 pression rather than transmission. 



Some of the i)rogenies of unbranched 

 plants having branched sibs related to 

 Init not of the above line plainly are 

 heterozygous for the branched charac- 

 ter while others seem homozygous for 

 its allelomorph but the ratio of heter- 

 ozygous to homozygous progenies is 

 not "orthodox. This behavior, however, 

 indicates that the branched character is 

 recessive to the normal form and per- 

 mits the prediction that all self -pollin- 

 ated branched ears will produce some 

 branched-eared plants l)Ut the uncer- 

 taintv w^ith which such plants appear 

 renders this character of little value in 

 testing linkages. The fact must not be 

 overlooked, however, that the mode of 

 inheritance of branched ears is charac- 

 teristic of a large class of characters 

 which seem so delicately balanced as to 

 require some special conditions in on- 

 togeny for complete expression. That 

 internal developmental factors, quite 

 aside from external influences, play a 

 large part in the expression of struc- 

 tural characters must be recognized and 

 the accumulation of data on the in- 

 heritance of the more regular charac- 

 ters should not be allowed to obscure 

 this fact. Such characters are to be 

 expected in view of the complicated 

 chemical reactions involved and should 

 not be urged as examples of non- 

 Mendelian inheritance e\'en though in 

 these cases the existence of stable he- 

 reditarv units can not be demonstrated. 



Mendelian Dominant, Or Maternal Impression? 



A schoolmaster wrote the following When the father signed the report 

 criticism on the edge of a boy's report and sent it back the card bore in ad- 

 card : "A good worker, but talks too dition to his signature this report: 

 much." "You should hear the mother." — Judge. 



