208 Dwarf Forms in Barley 



The above conclusion was perfectly confirmed by the following breeding 

 experiment : a certain number of seeds of ordinary dwarf plants were 

 sown in early spring 1919 instead of the autumn of the preceding j^ear 

 as it is usually the case in Japan. By this method I was enabled to 

 observe the segregation into three forms just discussed very easily, and 

 the numerical results were as follows : 



The ratio of the three types is approximately 1:2:1. The number 

 of sterile-dwarf plants, however, is in both cases somewhat smaller than 

 might be expected theoretically; this may be ascribed to the fact that they 

 die more easily than the others on account of their weak constitution. 



Thus we reach the conclusion that the dwarf plant which was found 

 at the beginning of my experiments was heterozygous with respect to the 

 characters in question, and that it was intermediate externally, i.e. smaller 

 than normal, but taller than sterile-dwarf In other words, if we denote 

 the allelomorph for dwarfness by D and its absence by d, we have sterile- 

 dwarf = DD, normal = dd, and ordinary dwarf = Dd. The seed which first 

 gave rise to the dwarf plant Dd may perhaps have arisen from dd by 

 mutation. Cases similar to ours have been observed in respect of dwarf 

 forms in plants. This is however the first case recorded in which the 

 sterile-dwarf has appeared in addition to the ordinary dwarf, 



EXPLANATION OF PLATE XX. 



Fig. 1. On the left two sterile-dwarf plants ; one plant in the middle is normal and two 



plants at right are ordinary dwarf types. 

 Fig. 2. In the middle is a normal plant and on either side are dwarf plants of the same 



type. The characters of these plants are very different from those shown in Fig. 1, 



and this is one of the three types mentioned on page 205. 



