167 
crowding might be expected to have some such effect as that 
observed. So far as known^ all other conditions uuder which these 
plants grew^ were conducive to vigorous development. At any 
rate this culture was in all other regards on an equal footing with 
the other cultures which were being grown during the same 
period^ and which gave normal development of the several 
biotypes. 
To test the Suggestion that crowding might be respon- 
sible for the failure of dominance, a second sowing was made 
on February 25, 1911, each seed being sown separately and 
spaced in such a manner that the seed-pan contained only 120 
plants. On April 7 these were potted and their growth has been 
continuously healthy and vigorous. They have not been subjected 
at any time to the least injurious crowding, yet they show the 
same tardy development of the tenuis characters as observed 
before. On April 22 only three of the 120 plants could be distin- 
guished from B. bp. sim; lex, though nearly all were sufficiently 
advanced that if it had been a normal family representing the same 
hybrid combination, almost a complete Separation of the alter- 
native types might have been made. The final census of the plants 
derived from this second sowing, made on the same basis and 
with the same care as in the case of the first sowing, showed 
85 B. bp. tenuis and 35 B. bp. simplex, — a ratio of 2.43 : 1. 
The conclusion is reached therefore that the low grade of the 
tenuis characters in this family is inherent, and not a direct 
effect of unfavorable conditions of the environment. 
This result appears to furnish an illustration of the phenom- 
enon known as „variable potency" but whether the gene Ä 
for the tenuis characters is really different in family 09275 from 
that in the other families must remain for the present an open 
question. It is conceivable that the relative inefficiency of Ä in 
this family is due to the Operation of some other factor which 
acts as a partial Inhibitor, so that al though the actual character 
of Ä remains unchanged, it must meet a greater resistance, and 
therefore produces a less effect. To avoid a decision of the 
question whether the gene has less power or whether it must 
meet a greater resistance, I use the expression „relative 
1) Davenport, C. B., Ileredity and Mendel's law. Proc. Wa^lhington 
Acad. Sei. 9:179 187, 31 Jy 1907.' 
