392 



MODIFIED CIRCUMXUTATION. 



Chap. VII 



Fig. 155. 



On the second day the descending Une zigzagged slightly. As 



usual, the ascending and de- 

 scending lines did not coincide. 

 On another occasion, when the 

 temperature was a little higlicr, 

 viz.; '2r- 2ti° C, a leaf was 

 observed 17 times between 8.50 

 A.M. and 12.16 p.m. ; it changed 

 its course by as much as a 

 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 

 rapidly and in a complex 

 manner. 



ACOTYLEDONS. 



Marsilea quadi ifuliala (Mar- 

 sTleacese). —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 

 merely accidental. The plant 

 was brought into a room, where 

 the temperature was only a little 

 above 60° F., and the movement 

 of one of the leaflets (the petiole 

 having been secured) was traced 



Hir-^phittm fiorHmndum : circumnu- 

 ■ tation and nyctitvopic movement 

 of a leaf, traced from 9 A.M. June 

 26thfo8.45 A.M. 27th ; filament 

 K.ied along the midrib. Ape.'! of 

 leaf SJ inches from the vertical 

 glass ; plant illuminated from 

 above. Temp. 23J°-24J° C. 



