M. WICHURA ON THE WINDING OF LEAVES. 287 



lateral direction in their course. In cosmical nature the planets 

 describe heliacal lines winding to the right in space, by virtue 

 of their circulation from west to east, since this is combined with 

 the advance, in company with the sun, toward a point in the 

 northern hemisphere. In the department of physics we meet 

 with allied phenomena in the circular polarization of light and 

 in the course of electro-magnetic spirals. Organic life exhibits 

 the same laws in the circulation of the blood, in all cases starting 

 from the left side of the animal body, and in the heliacal 

 windings of the shells of Mollusks, which follow a direction 

 determinate for every species. But plants above all give evi- 

 dence of a wonderful obedience to such laws, in the direction 

 of the spiral vessels, the heliacally winding trunks of trees, 

 winding stems and leaves, and probably also in the circulation 

 of their saps. In regard to the conceptions formed by the in- 

 tellect, it makes no difference at all in our views of the essential 

 nature of any force working in lateral direction, whether it sets 

 out towards the right or the left. In the rare cases in which 

 the human heart has been placed in the right side instead of the 

 left, it has been demonstrated that this anomaly did not interfere 

 with the vital powers of the body, Nevertheless, Nature, as 

 though dealing here with the most important business, displays 

 the most surprising regularity in this very lateral direction. 

 This apparent contradiction between our ideas and the phaeno- 

 mena of Nature has something in it so remarkable, that a rather 

 detailed account of observations on this particular point may 

 seem desirable. I shall therefore here subjoin my observations 

 on the direction peculiar to winding leaves, singly, in the order 

 of the Natural Families. This collocation will at the same time 

 serve to furnish a summary of the material of which I made use. 



55. 



Jungermanniaceae. Jungermannia Trichomanis, Dicks. : de- 

 hiscent valves of the fruit wound to the left. 



56. 



Musci frondosi. Cinclidotus fontinaloides ; Dichelyma falca- 

 tum ; Bartramia pomiformis, Hedw. ; Tortula ruralis, Swartz : 

 stem-leaves wound to the right. Cinclidotus 9 Barbula, and 



