392 



MODIFIED CIRCUMNUTATION. 



CHAP. VII. 



On the second day the descending line zigzagged slightly. As 

 p icr 165 usual, the ascending and de- 



" scending lines did not coincide. 



J On another occasion, when the 



i temperature was a little higher, 



/ viz., 24-26 C., a leaf was 



I observed 17 times between 8.50 



A.M. and 12.16 P.M. ; it changed 

 its course by as much as a 



I rectangle six times in this in- 



/ terval of 3 h. 26 m., and de- 



/ .scribed two irregular triangles 



/ and a half. The leaf, therefore, 



! on this occasion circumnutated 



japidly and in a complex 

 manner. 



ACOTYLEDONS. 



Marsilea quadiifoliata (Mar- 

 sileacese). The shape of a leaf, 

 expanded horizontally during 

 the day, is shown at A (Fig. 166). 

 Each leaflet is provided with 

 a well-developed pulvinus. 

 "When the leaves sleep, the two 

 terminal leaflets rise up, twist 

 half round and come into con- 

 tact with one another (B), and 

 are afterwards embraced by the 

 two lower leaflets (C); so that 

 the four leaflets with their lower 

 surfaces turned outwards form 

 a vertical packet. The curva- 

 ture of the summit of the petiole 

 of the leaf figured asleep, is 

 Strephium floribundwn : circumnu- merely accidental. The plant 

 tation and nyctitropic movement was brought into a room, where 

 &ttt^&V*t *e temperature was on] y a little 

 fixed along the midrib. Apex of above 60 F., and the movement 

 leaf at inches from the vertical o f one of the leaflets (the petiole 



P Tem * 2310 ** havin S been secured ) was traced 



