Chap. IV. MONOCOTYLEDONS. 255 



and had thus made the first step towards becoming dependent, 

 was traced orthogonically by the aid of a cube of wood (in the 

 manner before explained) ; and it was thus ascertained that the 

 actual distance traTelled by the apex, and due to circumnutation, 

 was 3| inches in the course of 20J h. During the next 24 h. it 

 travelled 2^ inches. The circumnutating movement, therefore, 

 of this young leaf was strongly marked. 



(30.) Paneratium littvrale (Amaryllideas). — The movements, 

 much magnified, of a leaf, 9 inches in length and inclined at 

 about 45° above the horizon, were traced during two days. On 

 the first day it changed its course completely, upwards and 

 downwards and laterally, 9 times in 12 h. ; and the figure traced 

 apparently represented five ellipses. On the second day it was 

 observed scldomer, and was therefore not seen to change its 

 course so often, viz., only 6 times, but in the same complex 

 manner as before. The movements were small in extent, but 

 there could bo no doubt about the circumnutation of the leaf. 



(31.) Jmatopliyllum- vel Clivia (sp. ?) (AmarylBdeae). — A long 

 glass filament was fixed to a leaf, and the angle formed by it 

 with the horizon was measured occasionally during three suc- 

 cessive days. It fell each morning until between 8 and 4 p.m., 

 and rose at night. The smallest angle at any time above the 

 horizon was 48°, and the largest 50° ; so that it rose only 2° 

 at night; but as this was observed each day, and as similar 

 observations were nightly made on another leaf on a distinct 

 plant, there can be no doubt that the leaves move periodically, 

 though to a very small extent. The position of the apex when 

 it stood highest was '8 of an inch above its lowest point. 



(32.) Pistia stratiotes (Aroideae, Fam. 30). — Hofmeister 

 remarks that the leaves of this floating water-plant are more 

 highly inclined at night than by day.* We therefore fastened 

 a fine glass filament to the midrib of a moderately young 

 leaf, and on Sept. 19th measured the angle which it formed 

 with the horizon 14 times between 9 a.m. an.d 11.50 p.m. The 

 temperature of the hot-house varied during the two days of 

 observation between 18i° and 235° C. At 9 a.m. the filament 

 stood at 32° above the horizon ; at 3.34 p.m. at 10° and at 

 11.50 P.M. at 55°; these two latter angles being the highest and 

 the lowest observed during the day, showing a difference of 45°. 

 The rising did not become strongly marked until between 



• ' Die Lehre von der Pflauzeczelle,' 1867, p. 327. 

 13 



