OCR Text |
Show 392 1\fODIFIED CIRCU1\1NUTATIO~. CHAP. VII. On the second day the descending line zigzagged slightly. As Fig. 165. usual, the ascending and deII /- ' i ! I ! I f I I I I ! I : ! Strephium flon'bundum: circumnu~ tation and nyctitropic movement of a leaf, traced from 9 A.M. June 26th to 8.45 A.M. 27th ; filament fixed along the midrib. Apex of leaf 8! inches from the vertical glass ; plant illuminated from above. Temp. 23~0-24~° C. scending lines did not coincide. On another occasion, when the temperature was a little higher, \iz., 24°-261° C., a leaf was obsened 17 times between 8.50 A.lii. and 12.16 P.M. ; it changed its course by as much as a rectangle six times in this interval of 3 b. 26 m., and described t"-·o irrecrn]ar triangles and a half. The leaf, therefore, on this occasion circumnutated rapidly and in a complex manner. A coTYLEDONS. 1J1a1·silea quadrifoUata (Marsileacero).- The shape of a leaf, expanded horizontally during the day, is shown at A (Fig.l6.6). Each leaflet is provided WJth 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 cur.m· ture of the summit of the petw~e of the leaf figmod asleep, IS merely accidental. Tho plant Was brou()'ht into a room, where the tempeor ature was only a rttle I a bovo 60o F.' and the movem.cnt of one of the leaflets (tho petJOl; having been secured) was trace CHAP. VII. SLEEP OF LEA VhS. 393 during 24 h. (Fig. 167). The leaf fell from tho early morning tilll.50 P.M., and then rose till 6 P.M., when it was asleep. A Fig. 166. A. B. c. Marst1ea quad1·ijoliala: A, leaf during the day, seen from vertically above· B, leaf beginning to go to sleep, seen laterally; C, the same asleep: Figures reduced to one-half of natural scale. , vertically dependent glaf:s filament was now fixed to one of tho terminal aml inner leaflets; and part of the tracing in Fig. 167, after 6 P.M., shows that it continu('d to sink, making one zigzag, nntil10.40 P.M. At 6.45 A.M. on the following morning, the leaf was awaking, and the filament pointed above the vertical glass, Fig. 167. 8" /J61a.tn.Btfi. ._ _______ '01(-- --- ----------------~ --------- 1DL!.'pm. 1'50'p.m. Marsilea quadrifuliat,~: circum nuta ~ion nnd nycti tropic movement of lea A et :~ced on vertical glass, durin o- nertrly 24 h. Figure r ed uced to tw~ lrds of original scale. Plant kept at rather too low a temperature. ~~t b~ 8.25 AM: it occupied the position shown in the figure. e .diagram differs greatly in appearance from most of those :re~ously given; and this is due to the leaflet twisting and OV!Dg laterally as it approaches and comes into contact with |