M. WICHURA ON THE WINDING OF LEAVES. 285 



winding stems are turned to the right in about the same pro- 

 portionate majority of cases, as the petals, at the other pole, are 

 wound to the left in the contorted aestivation. 



§51. 



The relations are somewhat different in the Mosses. As 

 already mentioned, the winding to the right occupies the upper 

 part, that to the left the lower part of the fruit- stalks of Mosses. 

 The winding fruit-stalks of the Mosses are further distinguished 

 from the leaves of Vascular plants by the circumstance that in 

 the latter the upper winding is developed before the lower, 

 while in the former the lower is shown before the upper. Since 

 then the lower winding of the fruit-stalk of the Mosses is directed 

 to the left and the upper to the right, the winding to the left 

 precedes that towards the right here also. The only exception 

 to this occurs in the fruit-stalks of the Funariece, which wind 

 to the right below and to the left above ; and in these, therefore, 

 the winding to the right precedes that towards the left. 



§ 52. 



A similar relation to that just demonstrated between the 

 winding to the left and right and the earlier and later, or upper 

 and lower parts of the leaf, may perhaps be assumed of the 

 w indings which derive their determination from the direction of 

 the leaf-spiral, either in the positive or negative sense. We are 

 led to this conjecture by the fact that leaves wound in the direc- 

 tion opposite to the leaf-spiral occur only in the contorted aesti- 

 vation, and leaves following the direction of the latter, only on 

 circles of stem -leaves, and perhaps the sepals of the family of 

 Cistineae. The contorted aestivation, on account of the wind- 

 ings, perfectly determinate in their direction in all cases, is espe- 

 cially important, as the principal seat of the upper winding, 

 from the fact that the wound flower-buds take the direction 

 toward the left in a preponderating multitude of cases. It is 

 very probable that a similar import is to be ascribed to it, to 

 that of windings determined in their direction by the leaf-spiral. 

 Under this hypothesis, therefore, we should have to regard the 

 winding contrary to the direction of the leaf-spiral as the upper 

 or earlier, the direction of the leaf- spiral as the lower and later. 



