534 
Heritable Spiral Torsions. 
node will become intercalated in the middle of an other- 
wise twisted stem. This can easily be seen in Fig. 125 
at a, in the gaping wound and in the vertically ascending 
longitudinal ribs. Sometimes nature itself makes a simi- 
Fig. 125. Dipsacus sylvestris torsus. 
The two leaves a and b of the twisted 
stem have been separated from one 
another in earliest youth by a cut : 
between them is seen the gaping split. 
The one leaf, b, is situated now about 
2 centimeters higher than the other, a. 
Above a the stem has remained straight 
for more than 2 centimeters. Some of 
the lower leaves were removed before 
photographing in order to show the 
important parts more clearly. 
lar experiment, and longitudinal growth tears the leaf- 
spiral in one or two places, without, however, making 
so deep a wound as results from an experiment. The 
result of such a natural experiment is a straight internode 
