The Significance of the Atavists. 555 
character, but that two antagonistic factors are at work, 
the one excluding the other, although never completely. 
Even the stems with the most pronounced torsions pro- 
duce branches, most of which revert to the decussate 
arrangement of leaves. It never occurs that this char- 
acter is completely excluded from the whole plant. Con- 
versely, as we have already seen, atavistic individuals 
with perfectly erect main stems and with a decussate or 
ternary arrangement of the leaves frequently exhibit 
torsions in their lateral branches. In 1887 I cut half the 
atavists of my culture of Dipsacus sylvestris torsus close 
clown to the ground ; they shot out from the base of the 
stem. In this way I obtained about 2000 branches of the 
second and third order. Amongst them 235 had a slight 
but quite definite torsion and 26 had a small many-leaved 
spiral. In the third generation I repeated the experiment 
with the same result ; and moreover observed torsions 
on the lateral branches of some atavists which had been 
allowed to remain on the beds until they were just about 
to flower. 
Other abnormalities in the arrangement of leaves also 
betray the real nature of the atavists. First, there are the 
individuals with ternary whorls. Such whorls do not 
occur in the early stages of the plant, and tricotylous 
seedlings are even very rare. At first the arrangement 
of the leaves is always decussate, and it is not until late 
summer or autumn, at the time when other specimens 
begin to produce their leaves in a spiral, that the decussate 
arrangement gives place to a ternary one. But when 
this has once appeared it usually remains on the stem 
up to the terminal flowerhead. Such plants look quite 
normal, and especially their leaves do not produce those 
forkings of the mid-rib which are so common in the 
