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 travelled by the apex, and due to circum nutation, 

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

 travelled 2s inches. The circumnutating movement, therefore, 

 of this young leaf was strongly marked. 



(30.) Pancratium littorale (Amaryllidese). 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 seldomer, 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 be no doubt about the circumnutation of the leaf. 



(31.) Imatophyllum. vel Olivia (sp. ?) (Amaryllidese). 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 3 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 (Aroidese, 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. and 11.50 P.M. The 

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

 observation between 18i and 23 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 Pflanzenzelle,' 1867, p. 327. 

 12 



