Chap, IV. CIECUMNUTATION OF LEAVES. 259 



was highly inclined, and the pot stood in front of a north-east 

 window. During the five first days the frond moved downwards 

 or became less inclined; and the long line which was traced 

 was strongly zigzag, with loops occasionally formed or nearly 

 formed ; and this indicated circumnutation. Whether the sink- 

 ing was due to epinastic growth, or apheliotropism, we do not 

 know. As the sinking was slight on the fifth day, a new tracing 

 was begun on the sixth day (Oct. 25th), and was continued 

 for 47 h. ; it is here given (Fig. 120). Another tracing was made 

 on the next day (27th) and the frond was found to be still cir- 

 cumnutating, for during 14 h. 30 m. it changed its course com- 

 pletely (besides minor changes) 10 times. It was casually 

 observed for two more days, and was seen to be continually 

 moving. 



The lowest members of the vegetable series, the Thallogens, 

 apparently circumnutate. If an Oscillaria be watched under 

 the microscope, it maybe seen to describe circles about every 

 40 seconds. After it has bent to one side, the tip first beginn 

 to bend back to the opposite side and then the whole filament 

 curves over in the same direction. Hofmeister* has given a 

 minute account of the curious, but less regular though constant, 

 movements of Spirogyra: during 2 J h. the filament moved 4 

 times to the left and 3 times to the right, and he refers to a 

 movement at right angles to the above. The tip moved at the 

 rate of about 0*1 mm. in five minutes. He compares the move- 

 ment with the nutation of the higher plants.f We shall hereafter 

 see that heliotropic movements result from modified circum- 

 nutation, and as unicellular Moulds bend to the light we may 

 infer that they also circumnutate. 



Concluding Eemarks on the Ciecumnutation 

 ov Leaves. 



The circumnutating movements of young leaves m 

 33 genera, belonging to 25 families, widely distributed 



* ' Ueber die Bewegungen cler 1880, vol. iil. p. 320) tliat the 



Faden der S/iirogyra prineeps : movements of Spirulina, a mem- 



.lahreshefte des Veieins t'iir vater- ber of the Osoillatorieae, are closely 



liindlsehe Naturkunde in Wurt- analogous "to the well-known 



teraberg,' 1874, p. 211. rotation of growing shoots and 



t Zukalalsoremarks (as quoted tendrils." 

 in 'Journal K. Mieroscop. Soo.,' 



