M. WICHURA ON THE WINDING OF LEAVES. 265 



II. Laws of Distribution. 



5. 



The relation of the winding to the outer form of the leaf, 

 mentioned in section I, gives the key to the laws of distribution 

 of the phenomenon. All alterations in the form of the leaf 

 connected with the proportion of the longitudinal to the trans- 

 verse growth, are consequently of importance in regard to the 

 occurrence of the winding movement. 



6. 



Even the single leaf displays changes of shape of this kind, 

 in its triple division into sheath, stalk, and blade. Winding 

 occurring in one of these parts is not therefore necessarily 

 imparted to the others, but is mostly limited within this. There 

 are many leaves with wound petioles and straight laminae, while, 

 on the contrary, in the stamens of Erythraea and other plants, 

 the lamina metamorphosed into an anther winds, while the 

 petiole, i. e. the filament, remains straight. Even within the 

 lamina itself, modifications of the curving movement occur, with 

 the expansions and contractions advancing from below upwards. 

 In such cases only the narrow parts wind, the broader not. 

 The broad ovate leaves of Paris quadrifolia, L., may be men- 

 tioned as an example, being straight as far as the attenuated 

 points which are wound slightly to the left. Leaves which 

 wind uniformly throughout their whole extent, exhibit the 

 corresponding perfect equality of transverse growth, from bottom 

 to top, as for instance the leaves of Typha latifolia, L., T. an- 

 gustifolia, L., and of many other Monocotyledons. 



7. 



The distribution of the winding movement in the different 

 leaves of the same axis depends on the same principles. Here 

 it is the metamorphoses of the leaf, known under the names of 

 cotyledons, stem-leaves, sepals, &c., which limit the winding 

 movement in virtue of their frequently totally different shapes. 

 It very frequently happens that the winding of the leaves is 



