A BRACHYTIC VARIATION" IN MAIZE. ' 6 



ties (No. Dh 416). The second generation, in which the brachytic 

 plants appeared, was the result of self -pollinating a first-generation 

 plant which was being grown for seed characters (10). Approxi- 

 mately one-quarter of the plants were brachytic, the actual numbers 

 being 5 brachytic and 21 normal (11). 



The appearance of brachytic plants in the second generation of 

 this hybrid may be explained by assuming that the Chinese parent 

 was heterozygous for brachysm. The reasons for this assumption 

 will appear later. On this hypothesis one-half of the F x plants 

 when self-pollinated should give progenies having one-quarter of 

 the plants brachytic, and if the Chinese parent had been self- 

 pollinated, one-quarter of its progeny also should be brachytic. 

 The Chinese plant, unfortunately, was not self-pollinated, so that 

 the possibility of its having been heterozygous for brachytic culms 

 can not be tested directly. However, many hundred progenies and 

 several large bulk plantings of this waxy variety have been grown 

 without brachytic plants having been found. It would seem, there- 

 fore, not unreasonable to conclude that this variation is the result 

 of a relatively recent genetic change and is not the result of bringing 

 into expression a recessive variation which has been masked by the 

 dominance of normal culms. 



The brachytic plants might also be accounted for by assuming that a 

 single gamete of the Chinese parent mutated and was fertilized by 

 a normal gamete of the Algerian variety, but since only three second 

 generation progenies of the hybrid Dh 416 have been grown, there is 

 a possibility that more than one gamete of the Chinese parent of this 

 hybrid had mutated. 



One of the brachytic plants was self-pollinated and the resulting 

 progeny were all brachytic. At the present time 16 progenies, de- 

 rived from self-pollination or crosses between sister brachytic plants, 

 have been grown. These progenies without exception have produced 

 nothing but brachytic plants. 



In addition to these 16 progenies several crosses have been made 

 between plants of normal stature and brachytic plants. The first 

 generations of such crosses were all as tall as or taller than the normal 

 parent, while the second generations show a segregation into normal 

 and brachytic plants closely approximating the Mendelian 3 to 1 

 ratio. 



Both parents of the hybrid from which the brachytic plants arose 

 may be considered of the pop-corn type and bear several small ears. 

 The brachytic plants are in no sense inferior to their parents in leaf 

 area or yield of grain. A comparison of normal and brachytic 

 progenies is shown in Table I. These progenies were grown from 

 self-pollinated ears of sister plants. 



