278 M^ WICHURA ON THE WINDING OF LEAVES. 



right border of each leaf covers the left of its neighbour, and 

 those where the opposite case occurs, as in fig. 1. no. 1, left- 

 wound. But the diagram fig. 2 shows that the flower-buds 

 which Linnaeus called right- wound owe their origin to a revolu- 

 tion of the individual leaflets to the left, and vice versd, I shall 

 therefore deviate from the terminology of Linnaeus in this point, 

 and call buds corresponding to the diagram figs. 1 & 2. no. 1. 

 right-wound,and those agreeing with figs. 1 & 2. no. 2. left-wound. 



IX. Direction of the Revolution around the Axis in reference to 

 the Systematic Divisions of the Vegetable Kingdom. 



§36. 



The direction in which leaves wind stands, like all the other 

 characters of plants, in a certain relation to the systematic sub- 

 divisions of the Vegetable Kingdom. Individuals of the same 

 species behave uniformly in the direction of the heliacally wound 

 leaves, and there are but few exceptions to this. Thus, for 

 instance, specimens of Medicago littoralisy Rohde, occur with 

 the legumes wound to the right and others with them wound to 

 the left. 



§37. 



Whole genera including only uniformly winding species are 

 somewhat rare. When the direction changes within the same 

 genus, the species which have like laws of direction may some- 

 times be arranged in common subsections of the genus from 

 agreement also in other essential characters. The genus Allium 

 furnishes a remarkable proof of this. The Allia with left-wound 

 stem-leaves, as A. acutangulum, Schrad., A. Moly, L., &c., with 

 perhaps the single exception of ^. azureum, Ledeb., all have a 

 leafless flowering stem, while right- wound stem- leaves occur 

 only in the species with a leafy flowering stem, as A» oleraceum, 

 L., A, sphoerocephalum, L., &c. 



§38. 



Natural families in which winding leaves are frequent, usually 

 include species the leaves of which wind in different directions, 

 but there are certain families in which a perfect agreement 

 exists ; the petals of the Ebenaceac, for instance, are in all cases 

 wound to the loll in the bud. 



