544 Heritable Spiral Torsions. 
ture, which extended over 18 years, I shall give here a 
brief summary of the nine successive generations. 
NUMBER OF PLANTS PER PROPORTION OF 
IjH,^ iSrv.A 1 IvJ^ 
PLANTS SQUARE METER TWISTED MAIN STEMS 
1st. 1884-1885 
2d. 1886-1887 1643 50 0.1 
3d. 1888-1889 1616 35 4 
4th. 1891-1892 107 25 34 
5th. 1893-1894 45 22 10 20 1 
6th. 1895-1896 33 8 42 
7th. 1897-1898 70 16 46 
8th. 1899-1900 1295 22 32 
9th. 1901-1902 492 22 41 
The mean of the six generations was therefore about 
35%. 
We see from this table that the continued isolation 
and selection of the finest torsions maintained the race 
at its level, but did not improve it to any considerable 
extent. 
Two points about this result should be noted. In the 
first place the percentage figures given do not denote the 
proportion of twisted individuals, but relate solely to 
those with torsions on the main stem. In some experi- 
ments, however, instead of pulling up the atavists, I only 
removed all their inflorescences before the flowers opened, 
and by this means I found that several, and often many of 
them, had the power of developing more or less fine local 
torsions on their lateral branches. In 1902 I made as 
accurate an account of these as possible, and found 71 
of them or 14%. Of twisted individuals there were, 
therefore, 41 -j- 14=5 5% altogether, i. e., somewhat more 
than half the individuals produced torsions. It seems 
of some interest to note that this percentage is the same 
1 The percentage figures for the 5th, 6th and 7th generations are 
hardly decisive on account of the small size of the cultures. 
