Spirally Twisted Races. 549 
of 16 individuals per square meter. Altogether there 
were 70 plants. 
A record made at the end of May 1898 gave the fol- 
lowing result : 
Twisted stems . . . . 32 =46% 
Ternary stems .... 21 =30% 
Decussate stems . 17 =24% 
Total 70 
In the eighth generation the plants were treated in 
exactly the same way as in the preceding one. As already 
mentioned, the offspring of 10 distinct parents were 
compared. Moreover for each parent the seeds of the 
terminal inflorescence were compared with those of the 
inflorescences on the main branches. For the latter de- 
termination I selected from each parent 4-8 of the strong- 
est branches which arose from that part of the middle 
of the stem which had undergone most torsion. They 
corresponded, therefore, with the period of maximum 
activity of the stem, 1 and confirmed this by the fact that 
small local torsions appeared on them. From the seed of 
the primary inflorescences I raised 645 plants with 31%, 
from those of the secondary inflorescences 650 individ- 
uals with 34% cwisted main stems. There was therefore 
no difference of any significance. 
The ninth generation was composed partly of off- 
spring of twisted individuals and partly of those of ata- 
vists. The method of culture employed was the same as 
before ; but I shall revert to the result of it in the next 
section. 
Besides Dipsacus sylvestris I have grown two other con- 
stant races with an abundance of fine torsions which must 
1 See T. TAMMES, Die Perlodicitat morphologischer Erschci- 
nungen bei den Pflanzen, Kon. Akad. v. Wet., Amsterdam, 1903. 
