548 THE PURE LINE HYPOTHESIS. 



very sharply distinguishable, and the habit of young plants only 

 could be thus differentiated. Even typically dwarf plants may 

 become more or less straggling as they grow old. When in a 

 comparatively young condition these plants were examined, and 

 the results were: 131 straggling or tall, 7 semi-dwarfs, and 42 

 dwarfs. 



On adding the semi-dwarfs to the dwarfs, we obtain 131 tall 

 and 49 with a tendency towards the dwarf condition. These 

 figures are not far from the j : i (i.e., 135 : 45) ratio. On dividing 

 the semi-dwarfs between the tall plants and the dwarf plants, we 

 have 134 tall and 46 dwarfs, and these figures are still closer to 

 the Mendelian ratio. 



Owing to the absence of a satisfactory measure of dwarfness, 

 a study of the inheritance of small variations in this character 

 was not undertaken. 



2. Variegation of the Leaves. 



The original seed-plant possessed large, uniform green leaves, 

 while the pollen-plant had small leaves, conspicuously spotted and 

 striped with yellowish-white. 



The 20 offspring obtained from the seed-plant by self- 

 fertilisation all had uniform green leaves, and the seven offspring 

 from the pollen-plant all had variegated leaves. Accordingly the 

 parent plants may be regarded as homozygous with respect to 

 these characters. 



The 21 offspring, or hybrids, obtained by crossing the above 

 plants all had perfectly green leaves. In two seedlings one or 

 two of the young leaves exhibited a few light spots, but it was not 

 possible to be certain whether these represented true variegation. 

 In any case all the subsequent leaves were perfectly green. Thus 

 uniform green leaves were dominant, and variegated leaves reces- 

 sive, and dominance appeared to be practically perfect. 



The 21 hybrids were self-fertilised and families were raised. 

 Some of the offspring w-ere green and some were variegated. 

 The amount of variegation observed in the variegated offspring 

 varied considerably, but there was never any doubt as to whether 

 any particular plant should be regarded as a variegated one or 

 not. The number of green offspring with no trace of variegation 

 was 135, and the number of variegated offspring was .SS- These 

 numbers diverge somewhat from the ratio of 3 : i (143 green, 47 

 variegated) ; there were too few variegated offspring, and the 

 divergence was in the wrong direction. In a somewhat similar 

 case cited by Bateson there were too few variegated offspring, and 

 he very plausibly suggested that this arose through the fact that 

 wholly variegated plants (i.e., those with no chlorophvll) would 

 be unable to live. Such an explanation will not fit the present 

 case, for if we suppose a certain number of plants did not survive 

 on account of lack of chlorophyll, the divergence from the typical 

 ratio would be still greater. 



There was a distinct tendency for the variation in the amount 

 of the variegation to remain similar in the different families, not- 



