Ohap. Vn. SLEEP OE LEAVES 389 



outwards. They are furnished, as might have been expected 

 from this complex kind of movement, with a pulvinus. 



Gymnospkkms. 



Pinus Nordmanniana (Coniferje). — M. Ohatin states * that the 

 leaves, ■which are horizontal during the day, rise up at night, so 

 a-! to assume a position almost perpendicular to the branch from 

 which they arise ; we presume that he here refers to a horizontal 

 branch. He adds : " En mfime temps, ce mouvement d'erection 

 est aocompagne d'un mouvement de torsion imprime a la partie 

 basilaire de la feuille, et poavant sou vent parcourir un arc de 

 90 degres." As the lower surfaces of the leaves are white, 

 whilst the upper are dark green, the tree presents a TOdely 

 different appearance by day and night. The leaves on a small 

 tree in a pot did not exhibit with us any nyctitropic move- 

 ments. We have seen in a former chapter that the leaves of 

 Pinus pinaster and Austriaca are continually circumnutating. 



Monocotyledons. 



Thalia dealbata (Cannaceee). — The leaves of this plant sleep 

 by turning vertically upwards ; they are furnished with a well- 

 developed pulvinus. It is the only instance known to us of 

 a very large leaf sleeping. The blade of a young leaf, which 

 was as yet only 13^ inches in length and 6Hn breadth, formed 

 at noon an angle with its tall petiole of 121°, and at night stood 

 vertically in a line with it, and so had risen 59°. The actual 

 distance travelled by the apex (as measured by an orthogonic 

 tracing) of another large leaf, between 7.30 a.m. and 10 p.m., was 

 lOi inches. The circumnutation of two young and dwarfed 

 leaves, arising amongst the taller leaves at the base of the plant, 

 was traced on a vertical glass during two days. On the first day 

 the apex of one, and on the second day the apex of the other leaf, 

 described between 6.40 a.m. and 4 p.m. two ellipses, the longer 

 axes of which were extended in very different directions from the 

 lines representing the great diurnal sinking and nocturnal rising 

 movement. 



Maranta arundinacea (Cannaoese). — The blades of the leaves, 

 which are furnished with a pulvinus, stand horizontally during 



' Comptes Rendus,' Jan. 1876, p. 171. 



