538 
Heritable Spiral Torsions. 
recall Dracocephalum moldavicum (Fig. 74, p. 369), 
Aspernla azurca, Centranthus macrosiphon and especially 
Mercurialis annua. In the latter species these malforma- 
tions appeared almost every year and often in consider- 
Fig. 126. Eqnisetiun Tclmatcja. Spiral torsion of an 
erect stem. 
able numbers, in mv tricotvlous and svncotvlons races 
* ^ > *> 
(Fig. 96, p. 464 J. 
Unless direct experiments in isolation have been made 
it is impossible in the majority of cases to be certain 
