286 M. WICnURA ON THE WINDING OF LEAVES. 



XII. Direction of Winding Leaves in relation to the Direction 



of the Winding Stem. 



53. 



The movement of winding displays itself in two different forms 

 in the stems of plants. There are stems which by their move- 

 ment twine round a support, and stems which, like winding 

 leaves, complete their movement in freedom without twining 

 round a prop. The remark made above, that stems, as structures 

 situated below, wind predominantly toward the right, and thus 

 form a contrast to the blades of the stem-leaves more frequently 

 winding to the left, holds good, as it remarkably appears, only 

 of winding stems of the former kind. The hitherto little-known 

 winding stems of the latter kind, which occur not unfrequently 

 in the Monocotyledons, wind always in the direction in which 

 the stem-leaves of these plants are \vound. Thus we find left- 

 wound flower-stems and stem-leaves in Eleocharis palustris, 

 R. Br., Fam. of Cyperaceae ; in all the species of Xyris, Fam. of 

 Xyridaceae, with which I am acquainted ; in Butomus umbella- 

 tus, Fam. of Butomese ; Allium acutangulum, Schrd. ; All.fallax, 

 Don ; All. ursinum, L. ; All. Stellerianum, Willd. ; AH.flaves- 

 cenSy Bess. ; Tulbaghia alliacea, L. ; T. cepacea, L., Fam. of 

 Liliaceae; Leucojum cestivum, L., Fam. of Amaryllideae. Right- 

 wound flowering- stems and stem-leaves in Aristidea megapota- 

 mica, Spr., Fam. of Gramineae ; P&palanthus perpusillus, Kl. ; 

 P. Ottonis, KL, Fam. of Eriocauloneae; MorceafiliformiSjThurib., 

 Fam. of Irideae. Lastly, in Sisirynchium anceps, belonging to 

 the family of the Irideas, the leaves and stems of some speci- 

 mens wind to the right, those of others to the left, so that in 

 spite of the change of direction occurring in the same species, 

 leaves and stem are always wound toward the same side in the 

 same individual. 



XIII. Individual observations on the Direction of the convolution 

 round the axis, collocated in the order of the Natural Families. 



54. 



It is a very remarkable phenomenon that the circularly or 

 heliacally acting forces of nature follow an unchanging, definite 



