192 
NATURE NOTES 
movement and abnormal spiral torsion are more relevant to 
this present case. Darwin showed that, while “ dorsi-ventral ” 
horizontal structures, such as ordinary foliage-leaves, may 
“ nutate,” or change their direction of growth, once or twice 
“ simply,” growing faster below and then faster above, and 
while vertical leaves, such as those of the Reed-mace (Tyfiha), 
may nutate repeatedlv but simply, elongating from side to side 
in an upward zig-zag movement, stems, tendrils, and other 
structures, which are cylindric or round in section, commonly 
“ circum-nutate.” Elongating, that is to say, as it were, in 
a succession of jerks at each successive point in their circum- 
ference, their apex describes an upward spiral, the sweep of 
Spiral Torsion in Cedar at Dulwich. 
(From Photograph by Mrs. J. J. H, Teall.) 
which depends upon their flexibility. The intervention of an 
obstacle within the sweep of this circumnutation brings about 
the spiral twining of numerous climbing-plants, which twining 
is frequently accompanied by torsion, or twisting of the stem 
about its own axis. When that remarkable fusion of several 
stems together into a broad ribbon-like structure, which we 
call “ fasciation,” occurs, as it often does in the stems of 
Teazles or in the branches of the Holly, it appears as if the 
checked circumnutation produced the spiral torsion, which is the 
frequent concomitant of fasciation. Some years ago, teazle- 
