8o 



The Journal of Heredity 



and tip kernels. Usually, however, 

 the dimple or crease is much more pro- 

 nounced than in ordinary dent corn. 

 The shrinking from the sides of the 

 kernel presents a condition which the 

 writer has never observed in dent corn, 

 the indentation of which is usually 

 rough and always at the top. The most 

 striking difference in the two types of 

 indentation aside from one of degree is 

 the fact that in shrunken kernels a 

 cavity is usually found within the upper 

 part of the endospenn as if the cells in 

 this region had not been filled with 

 starch as the kernel matured (See 

 Figure 24.) Previous to the hard 

 dough stage shrunken kernels are 

 smooth and rounded in outline. As 

 they begin to dry the top or sides sink 

 in to such an extent at times that the 

 cavity is closed altho its outline may be 

 distinctly seen. In other cases, par- 

 ticularly where there is a fairly thick 

 layer of corneous starch at the top of 

 the kernel the latter may be almost 

 smooth in outline. In such kernels the 

 cavity beneath the shell of corneous 

 starch is very pronounced. On the 

 other hand, in dent corn the endosperm 

 is filled, the indentation being due to a 

 greater shrinking of the soft starch at 

 the top of the kernel than of the corne- 

 ous starch on the sides. 



By reason of this fact, little difificulty 

 has been found in distinguishing 

 shrunken from non-shrunken kernels 

 with starchy endosperm. It is difficult, 

 however, always to classify shrunken 

 and non-shrunken kernels in sweet 

 corn, particularly on ears of the 

 Country Gentlemen type where the 

 kernels are long, narrow and pointed 

 and very irregular in shape. Such 

 separations are much more readily 

 made on eight or ten rowed ears of 

 sweet corn where the kernels are broad 

 and rounded and fairly regular in out- 

 line. 



In examining shrunken and non- 

 shrunken kernels one is apt to gain 

 the impression that the former are 

 lighter in weight than the latter since 

 they are apparently not fully devel- 

 oped. This, however, is not the case. 

 Data obtained by weighing the 



shrunken and non-shrunken kernels on 

 the ears from six Fj plants that had 

 been backcrossed to shrunken show 

 that while the non-shrunken kernels are 

 slightly heavier the difference is not 

 statistically significant. These data are 

 given in the following table: 



Non-shrunken 

 Shrunken 



Difference 



Number of 



kernels 



weighed 



914 



874 



A verage weight 

 oj kernels 



272+ 8.42 mg. 

 259 ± 10.89 mg. 



13 ± 13.76 mg. 



INHERITANCE OF SHRUNKEN 

 ENDOSPERM 



As Stated above the character 

 shrunken endosperm is inherited as a 

 simple recessive to the normal or non- 

 shrunken. Numerous crosses have 

 been made between shrunken and non- 

 shrunken plants and the Fi seeds pro- 

 duced have been normal in all cases. 

 A number of such hybrid kernels have 

 been planted and the resulting plants 

 selfed for F2 progenies. Two such 

 progenies consisted of 705 non-shrunken 

 and 239 shrunken kernels. This is a 

 deviation of only 3 ± 8.97 seeds from 

 the 3: 1 relation expected when the 

 parents differ in a single pair of factors. 

 A number of Fi plants also were back- 

 crossed with the recessive shrunken in 

 connection with some linkage studies 

 to be described later. A total of 20,556 

 kernels resulting from such backcrosses 

 have been examined, of which 10,295 

 were shrunken and 10,261 non- 

 shrunken. This is a deviation of only 

 17 ± 48 . 3 seeds from the 1 : 1 ratio 

 expected. Evidently shrunken en- 

 dosperm is differentiated from the 

 normal by the single factor pair Sh sh. 



LINKAGE RELATIONS OF Sh sh AND IVx 



WX, AND Sh sh AND THE ALEURONE 



FACTORS C C AND / t 



The fact that waxy endospenn and 

 aleurone color in maize are linked was 

 first established bv Collins and Kemp- 

 ton (1911). Bregger (1918) was able 

 to show that the particular aleurone 

 color factor concerned is the C c pair. 

 Among the crosses made by Dr. Emer- 

 son in 1918 with shrunken one involved 



