474 The Ohio Naturalist. [Vol. XII, No. 4, 



THE DIURNALlNODDING OF THE WILD CARROT AND 



OTHER PLANTS. 



John H. Schaffner. 



Many plants exhibit periodical movements during the twenty- 

 four hours of a day. Among the more interesting of such move- 

 ments is the daily nodding in the evening, shown by a number of 

 species common along the roadside. 



During the past summer the writer obtained considerable 

 pleasure in making observations on some of the common plants of 

 Columbus. One of the most striking in this respect is the wild 

 carrot (Daucus carota L.) In thrifty plants there are usually a 

 number of branches which all begin to nod at an early age and 

 continue the habit until the plant is in full bloom. The best time 

 to study this peculiar jjhenomenon is from the middle of June to 

 the middle of July. The long peduncles, bearing the young 

 umbels nod before the sun goes down, the curving being prominent 

 by six o'clock. The various branches nod in a radial manner 

 outward from the central axis of the plant. The length of time 

 taken to develop the curve was not ascertained but it was 

 observed that the peduncles are erect in the morning and remain 

 so during the day. Late in the afternoon, the curving begins and 

 continues until in some cases the peduncle describes nearly a 

 circle. The nodding is most striking just before the blooming 

 period in plants with numerous long peduncles. At this period 

 the umbel frequently moves through an angle of over 270°. 

 Frequently the upper face of the umbel touches the side of the 

 peduncle. The diameter of the curve in a medium sized peduncle 

 is about two inches. The curved peduncle is quite rigid and should 

 show an interesting cellular condition if properly studied. The 

 diurnal nodding of the peduncle stops at the time of anthesis, 

 although there are subsequent interesting movements in the rays 

 of the umbel itself at a later period. 



The common Dogfennel (Anthemis cotula L.) also has the 

 diurnal nodding habit. Its numerous lateral branches bearing 

 heads of flowers nod in the evening and at night and become erect 

 again early in the morning. The nodding takes place in the 

 same radial manner as in the wild carrot. 



In Lactuca hirsuta Muhl., before and dviring anthesis a decided 

 drooping or nodding of the large flower cluster occurs, the main 

 axis bending about six inches from the tip. The stems were 

 found erect in the morning. Euphorbia nutans Lag., as its 

 name indicates, also has a nodding of the tips of the stems each 

 evening and a return to the erect position in the morning. 



One may well ask as to the purpose of the nodding habit so 

 prominently developed in the wild carrot. Is the cause of the 



