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 wonnd and in tlie vertically ascending 

 longitudinal ribs. Sometimes nature itself makes a simi- 



Fig. 125. Dipsaciis sylvcstris torsiis. 

 The two leaves a and h of the twisted 

 stem have been separated from one 

 another in earliest youth by a cut : 

 between them is seen the gaping spht. 

 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 expernnent. The 

 result of such a natural experiment is a straight internode 



